Add hooking ability for producing help mime bundle. (#14300)

I plan to use this for papyri in order to send the right informations to
the frontend.

IPython/core/oinspect.py

@@ -1,1170 +1,1183
-# -*- coding: utf-8 -*-
 """Tools for inspecting Python objects.
 
 Uses syntax highlighting for presenting the various information elements.
 
 Similar in spirit to the inspect module, but all calls take a name argument to
 reference the name under which an object is being read.
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 __all__ = ['Inspector','InspectColors']
 
 # stdlib modules
 from dataclasses import dataclass
 from inspect import signature
 from textwrap import dedent
 import ast
 import html
 import inspect
 import io as stdlib_io
 import linecache
 import os
-import sys
 import types
 import warnings
 
 from typing import Any, Optional, Dict, Union, List, Tuple
 
 from typing import TypeAlias
 
+import traitlets
+
 # IPython's own
 from IPython.core import page
 from IPython.lib.pretty import pretty
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import PyColorize
 from IPython.utils import openpy
 from IPython.utils.dir2 import safe_hasattr
 from IPython.utils.path import compress_user
 from IPython.utils.text import indent
 from IPython.utils.wildcard import list_namespace
 from IPython.utils.wildcard import typestr2type
-from IPython.utils.coloransi import TermColors, ColorScheme, ColorSchemeTable
+from IPython.utils.coloransi import TermColors
 from IPython.utils.py3compat import cast_unicode
 from IPython.utils.colorable import Colorable
 from IPython.utils.decorators import undoc
 
 from pygments import highlight
 from pygments.lexers import PythonLexer
 from pygments.formatters import HtmlFormatter
 
 HOOK_NAME = "__custom_documentations__"
 
 
 UnformattedBundle: TypeAlias = Dict[str, List[Tuple[str, str]]]  # List of (title, body)
 Bundle: TypeAlias = Dict[str, str]
 
 
 @dataclass
 class OInfo:
     ismagic: bool
     isalias: bool
     found: bool
     namespace: Optional[str]
     parent: Any
     obj: Any
 
     def get(self, field):
         """Get a field from the object for backward compatibility with before 8.12
 
         see https://github.com/h5py/h5py/issues/2253
         """
         # We need to deprecate this at some point, but the warning will show in completion.
         # Let's comment this for now and uncomment end of 2023 ish
         #        warnings.warn(
         #            f"OInfo dataclass with fields access since IPython 8.12 please use OInfo.{field} instead."
         #            "OInfo used to be a dict but a dataclass provide static fields verification with mypy."
         #            "This warning and backward compatibility `get()` method were added in 8.13.",
         #            DeprecationWarning,
         #            stacklevel=2,
         #        )
         return getattr(self, field)
 
 
 def pylight(code):
     return highlight(code, PythonLexer(), HtmlFormatter(noclasses=True))
 
 # builtin docstrings to ignore
 _func_call_docstring = types.FunctionType.__call__.__doc__
 _object_init_docstring = object.__init__.__doc__
 _builtin_type_docstrings = {
     inspect.getdoc(t) for t in (types.ModuleType, types.MethodType,
                                 types.FunctionType, property)
 }
 
 _builtin_func_type = type(all)
 _builtin_meth_type = type(str.upper)  # Bound methods have the same type as builtin functions
 #****************************************************************************
 # Builtin color schemes
 
 Colors = TermColors  # just a shorthand
 
 InspectColors = PyColorize.ANSICodeColors
 
 #****************************************************************************
 # Auxiliary functions and objects
 
 # See the messaging spec for the definition of all these fields.  This list
 # effectively defines the order of display
 info_fields = ['type_name', 'base_class', 'string_form', 'namespace',
                'length', 'file', 'definition', 'docstring', 'source',
                'init_definition', 'class_docstring', 'init_docstring',
                'call_def', 'call_docstring',
                # These won't be printed but will be used to determine how to
                # format the object
                'ismagic', 'isalias', 'isclass', 'found', 'name'
                ]
 
 
 def object_info(**kw):
     """Make an object info dict with all fields present."""
     infodict = {k:None for k in info_fields}
     infodict.update(kw)
     return infodict
 
 
 def get_encoding(obj):
     """Get encoding for python source file defining obj
 
     Returns None if obj is not defined in a sourcefile.
     """
     ofile = find_file(obj)
     # run contents of file through pager starting at line where the object
     # is defined, as long as the file isn't binary and is actually on the
     # filesystem.
     if ofile is None:
         return None
     elif ofile.endswith(('.so', '.dll', '.pyd')):
         return None
     elif not os.path.isfile(ofile):
         return None
     else:
         # Print only text files, not extension binaries.  Note that
         # getsourcelines returns lineno with 1-offset and page() uses
         # 0-offset, so we must adjust.
         with stdlib_io.open(ofile, 'rb') as buffer:   # Tweaked to use io.open for Python 2
-            encoding, lines = openpy.detect_encoding(buffer.readline)
+            encoding, _lines = openpy.detect_encoding(buffer.readline)
         return encoding
 
 def getdoc(obj) -> Union[str,None]:
     """Stable wrapper around inspect.getdoc.
 
     This can't crash because of attribute problems.
 
     It also attempts to call a getdoc() method on the given object.  This
     allows objects which provide their docstrings via non-standard mechanisms
     (like Pyro proxies) to still be inspected by ipython's ? system.
     """
     # Allow objects to offer customized documentation via a getdoc method:
     try:
         ds = obj.getdoc()
     except Exception:
         pass
     else:
         if isinstance(ds, str):
             return inspect.cleandoc(ds)
     docstr = inspect.getdoc(obj)
     return docstr
 
 
 def getsource(obj, oname='') -> Union[str,None]:
     """Wrapper around inspect.getsource.
 
     This can be modified by other projects to provide customized source
     extraction.
 
     Parameters
     ----------
     obj : object
         an object whose source code we will attempt to extract
     oname : str
         (optional) a name under which the object is known
 
     Returns
     -------
     src : unicode or None
 
     """
 
     if isinstance(obj, property):
         sources = []
         for attrname in ['fget', 'fset', 'fdel']:
             fn = getattr(obj, attrname)
             if fn is not None:
                 encoding = get_encoding(fn)
                 oname_prefix = ('%s.' % oname) if oname else ''
                 sources.append(''.join(('# ', oname_prefix, attrname)))
                 if inspect.isfunction(fn):
                     _src = getsource(fn)
                     if _src:
                         # assert _src is not None, "please mypy"
                         sources.append(dedent(_src))
                 else:
                     # Default str/repr only prints function name,
                     # pretty.pretty prints module name too.
                     sources.append(
                         '%s%s = %s\n' % (oname_prefix, attrname, pretty(fn))
                     )
         if sources:
             return '\n'.join(sources)
         else:
             return None
 
     else:
         # Get source for non-property objects.
 
         obj = _get_wrapped(obj)
 
         try:
             src = inspect.getsource(obj)
         except TypeError:
             # The object itself provided no meaningful source, try looking for
             # its class definition instead.
             try:
                 src = inspect.getsource(obj.__class__)
             except (OSError, TypeError):
                 return None
         except OSError:
             return None
 
         return src
 
 
 def is_simple_callable(obj):
     """True if obj is a function ()"""
     return (inspect.isfunction(obj) or inspect.ismethod(obj) or \
             isinstance(obj, _builtin_func_type) or isinstance(obj, _builtin_meth_type))
 
 @undoc
 def getargspec(obj):
     """Wrapper around :func:`inspect.getfullargspec`
 
     In addition to functions and methods, this can also handle objects with a
     ``__call__`` attribute.
 
     DEPRECATED: Deprecated since 7.10. Do not use, will be removed.
     """
 
     warnings.warn('`getargspec` function is deprecated as of IPython 7.10'
                   'and will be removed in future versions.', DeprecationWarning, stacklevel=2)
 
     if safe_hasattr(obj, '__call__') and not is_simple_callable(obj):
         obj = obj.__call__
 
     return inspect.getfullargspec(obj)
 
 @undoc
 def format_argspec(argspec):
     """Format argspect, convenience wrapper around inspect's.
 
     This takes a dict instead of ordered arguments and calls
     inspect.format_argspec with the arguments in the necessary order.
 
     DEPRECATED (since 7.10): Do not use; will be removed in future versions.
     """
     
     warnings.warn('`format_argspec` function is deprecated as of IPython 7.10'
                   'and will be removed in future versions.', DeprecationWarning, stacklevel=2)
 
 
     return inspect.formatargspec(argspec['args'], argspec['varargs'],
                                  argspec['varkw'], argspec['defaults'])
 
 @undoc
 def call_tip(oinfo, format_call=True):
     """DEPRECATED since 6.0. Extract call tip data from an oinfo dict."""
     warnings.warn(
         "`call_tip` function is deprecated as of IPython 6.0"
         "and will be removed in future versions.",
         DeprecationWarning,
         stacklevel=2,
     )
     # Get call definition
     argspec = oinfo.get('argspec')
     if argspec is None:
         call_line = None
     else:
         # Callable objects will have 'self' as their first argument, prune
         # it out if it's there for clarity (since users do *not* pass an
         # extra first argument explicitly).
         try:
             has_self = argspec['args'][0] == 'self'
         except (KeyError, IndexError):
             pass
         else:
             if has_self:
                 argspec['args'] = argspec['args'][1:]
 
         call_line = oinfo['name']+format_argspec(argspec)
 
     # Now get docstring.
     # The priority is: call docstring, constructor docstring, main one.
     doc = oinfo.get('call_docstring')
     if doc is None:
         doc = oinfo.get('init_docstring')
     if doc is None:
         doc = oinfo.get('docstring','')
 
     return call_line, doc
 
 
 def _get_wrapped(obj):
     """Get the original object if wrapped in one or more @decorators
 
     Some objects automatically construct similar objects on any unrecognised
     attribute access (e.g. unittest.mock.call). To protect against infinite loops,
     this will arbitrarily cut off after 100 levels of obj.__wrapped__
     attribute access. --TK, Jan 2016
     """
     orig_obj = obj
     i = 0
     while safe_hasattr(obj, '__wrapped__'):
         obj = obj.__wrapped__
         i += 1
         if i > 100:
             # __wrapped__ is probably a lie, so return the thing we started with
             return orig_obj
     return obj
 
-def find_file(obj) -> str:
+def find_file(obj) -> Optional[str]:
     """Find the absolute path to the file where an object was defined.
 
     This is essentially a robust wrapper around `inspect.getabsfile`.
 
     Returns None if no file can be found.
 
     Parameters
     ----------
     obj : any Python object
 
     Returns
     -------
     fname : str
         The absolute path to the file where the object was defined.
     """
     obj = _get_wrapped(obj)
 
-    fname = None
+    fname: Optional[str] = None
     try:
         fname = inspect.getabsfile(obj)
     except TypeError:
         # For an instance, the file that matters is where its class was
         # declared.
         try:
             fname = inspect.getabsfile(obj.__class__)
         except (OSError, TypeError):
             # Can happen for builtins
             pass
     except OSError:
         pass
 
-    return cast_unicode(fname)
+    return fname
 
 
 def find_source_lines(obj):
     """Find the line number in a file where an object was defined.
 
     This is essentially a robust wrapper around `inspect.getsourcelines`.
 
     Returns None if no file can be found.
 
     Parameters
     ----------
     obj : any Python object
 
     Returns
     -------
     lineno : int
         The line number where the object definition starts.
     """
     obj = _get_wrapped(obj)
 
     try:
         lineno = inspect.getsourcelines(obj)[1]
     except TypeError:
         # For instances, try the class object like getsource() does
         try:
             lineno = inspect.getsourcelines(obj.__class__)[1]
         except (OSError, TypeError):
             return None
     except OSError:
         return None
 
     return lineno
 
 class Inspector(Colorable):
 
-    def __init__(self, color_table=InspectColors,
+    mime_hooks = traitlets.Dict(
+        config=True,
+        help="dictionary of mime to callable to add informations into help mimebundle dict",
+    ).tag(config=True)
+
+    def __init__(
+        self,
+        color_table=InspectColors,
                  code_color_table=PyColorize.ANSICodeColors,
                  scheme=None,
                  str_detail_level=0,
-                 parent=None, config=None):
+        parent=None,
+        config=None,
+    ):
         super(Inspector, self).__init__(parent=parent, config=config)
         self.color_table = color_table
         self.parser = PyColorize.Parser(out='str', parent=self, style=scheme)
         self.format = self.parser.format
         self.str_detail_level = str_detail_level
         self.set_active_scheme(scheme)
 
     def _getdef(self,obj,oname='') -> Union[str,None]:
         """Return the call signature for any callable object.
 
         If any exception is generated, None is returned instead and the
         exception is suppressed."""
         if not callable(obj):
             return None
         try:
             return _render_signature(signature(obj), oname)
         except:
             return None
 
     def __head(self,h) -> str:
         """Return a header string with proper colors."""
         return '%s%s%s' % (self.color_table.active_colors.header,h,
                            self.color_table.active_colors.normal)
 
     def set_active_scheme(self, scheme):
         if scheme is not None:
             self.color_table.set_active_scheme(scheme)
             self.parser.color_table.set_active_scheme(scheme)
 
     def noinfo(self, msg, oname):
         """Generic message when no information is found."""
         print('No %s found' % msg, end=' ')
         if oname:
             print('for %s' % oname)
         else:
             print()
 
     def pdef(self, obj, oname=''):
         """Print the call signature for any callable object.
 
         If the object is a class, print the constructor information."""
 
         if not callable(obj):
             print('Object is not callable.')
             return
 
         header = ''
 
         if inspect.isclass(obj):
             header = self.__head('Class constructor information:\n')
 
 
         output = self._getdef(obj,oname)
         if output is None:
             self.noinfo('definition header',oname)
         else:
             print(header,self.format(output), end=' ')
 
     # In Python 3, all classes are new-style, so they all have __init__.
     @skip_doctest
     def pdoc(self, obj, oname='', formatter=None):
         """Print the docstring for any object.
 
         Optional:
         -formatter: a function to run the docstring through for specially
         formatted docstrings.
 
         Examples
         --------
         In [1]: class NoInit:
            ...:     pass
 
         In [2]: class NoDoc:
            ...:     def __init__(self):
            ...:         pass
 
         In [3]: %pdoc NoDoc
         No documentation found for NoDoc
 
         In [4]: %pdoc NoInit
         No documentation found for NoInit
 
         In [5]: obj = NoInit()
 
         In [6]: %pdoc obj
         No documentation found for obj
 
         In [5]: obj2 = NoDoc()
 
         In [6]: %pdoc obj2
         No documentation found for obj2
         """
 
         head = self.__head  # For convenience
         lines = []
         ds = getdoc(obj)
         if formatter:
             ds = formatter(ds).get('plain/text', ds)
         if ds:
             lines.append(head("Class docstring:"))
             lines.append(indent(ds))
         if inspect.isclass(obj) and hasattr(obj, '__init__'):
             init_ds = getdoc(obj.__init__)
             if init_ds is not None:
                 lines.append(head("Init docstring:"))
                 lines.append(indent(init_ds))
         elif hasattr(obj,'__call__'):
             call_ds = getdoc(obj.__call__)
             if call_ds:
                 lines.append(head("Call docstring:"))
                 lines.append(indent(call_ds))
 
         if not lines:
             self.noinfo('documentation',oname)
         else:
             page.page('\n'.join(lines))
 
     def psource(self, obj, oname=''):
         """Print the source code for an object."""
 
         # Flush the source cache because inspect can return out-of-date source
         linecache.checkcache()
         try:
             src = getsource(obj, oname=oname)
         except Exception:
             src = None
 
         if src is None:
             self.noinfo('source', oname)
         else:
             page.page(self.format(src))
 
     def pfile(self, obj, oname=''):
         """Show the whole file where an object was defined."""
 
         lineno = find_source_lines(obj)
         if lineno is None:
             self.noinfo('file', oname)
             return
 
         ofile = find_file(obj)
         # run contents of file through pager starting at line where the object
         # is defined, as long as the file isn't binary and is actually on the
         # filesystem.
         if ofile.endswith(('.so', '.dll', '.pyd')):
             print('File %r is binary, not printing.' % ofile)
         elif not os.path.isfile(ofile):
             print('File %r does not exist, not printing.' % ofile)
         else:
             # Print only text files, not extension binaries.  Note that
             # getsourcelines returns lineno with 1-offset and page() uses
             # 0-offset, so we must adjust.
             page.page(self.format(openpy.read_py_file(ofile, skip_encoding_cookie=False)), lineno - 1)
 
 
     def _mime_format(self, text:str, formatter=None) -> dict:
         """Return a mime bundle representation of the input text.
 
         - if `formatter` is None, the returned mime bundle has
            a ``text/plain`` field, with the input text.
            a ``text/html`` field with a ``<pre>`` tag containing the input text.
 
         - if ``formatter`` is not None, it must be a callable transforming the
           input text into a mime bundle. Default values for ``text/plain`` and
           ``text/html`` representations are the ones described above.
 
         Note:
 
         Formatters returning strings are supported but this behavior is deprecated.
 
         """
         defaults = {
             "text/plain": text,
             "text/html": f"<pre>{html.escape(text)}</pre>",
         }
 
         if formatter is None:
             return defaults
         else:
             formatted = formatter(text)
 
             if not isinstance(formatted, dict):
                 # Handle the deprecated behavior of a formatter returning
                 # a string instead of a mime bundle.
                 return {"text/plain": formatted, "text/html": f"<pre>{formatted}</pre>"}
 
             else:
                 return dict(defaults, **formatted)
 
     def format_mime(self, bundle: UnformattedBundle) -> Bundle:
         """Format a mimebundle being created by _make_info_unformatted into a real mimebundle"""
         # Format text/plain mimetype
         assert isinstance(bundle["text/plain"], list)
         for item in bundle["text/plain"]:
             assert isinstance(item, tuple)
 
         new_b: Bundle = {}
         lines = []
         _len = max(len(h) for h, _ in bundle["text/plain"])
 
         for head, body in bundle["text/plain"]:
             body = body.strip("\n")
             delim = "\n" if "\n" in body else " "
             lines.append(
                 f"{self.__head(head+':')}{(_len - len(head))*' '}{delim}{body}"
             )
 
         new_b["text/plain"] = "\n".join(lines)
 
         if "text/html" in bundle:
             assert isinstance(bundle["text/html"], list)
             for item in bundle["text/html"]:
                 assert isinstance(item, tuple)
             # Format the text/html mimetype
             if isinstance(bundle["text/html"], (list, tuple)):
                 # bundle['text/html'] is a list of (head, formatted body) pairs
                 new_b["text/html"] = "\n".join(
                     (f"<h1>{head}</h1>\n{body}" for (head, body) in bundle["text/html"])
                 )
 
         for k in bundle.keys():
             if k in ("text/html", "text/plain"):
                 continue
             else:
                 new_b = bundle[k]  # type:ignore
         return new_b
 
     def _append_info_field(
         self,
         bundle: UnformattedBundle,
         title: str,
         key: str,
         info,
         omit_sections,
         formatter,
     ):
         """Append an info value to the unformatted mimebundle being constructed by _make_info_unformatted"""
         if title in omit_sections or key in omit_sections:
             return
         field = info[key]
         if field is not None:
             formatted_field = self._mime_format(field, formatter)
             bundle["text/plain"].append((title, formatted_field["text/plain"]))
             bundle["text/html"].append((title, formatted_field["text/html"]))
 
     def _make_info_unformatted(
         self, obj, info, formatter, detail_level, omit_sections
     ) -> UnformattedBundle:
         """Assemble the mimebundle as unformatted lists of information"""
         bundle: UnformattedBundle = {
             "text/plain": [],
             "text/html": [],
         }
 
         # A convenience function to simplify calls below
         def append_field(
             bundle: UnformattedBundle, title: str, key: str, formatter=None
         ):
             self._append_info_field(
                 bundle,
                 title=title,
                 key=key,
                 info=info,
                 omit_sections=omit_sections,
                 formatter=formatter,
             )
 
         def code_formatter(text) -> Bundle:
             return {
                 'text/plain': self.format(text),
                 'text/html': pylight(text)
             }
 
         if info["isalias"]:
             append_field(bundle, "Repr", "string_form")
 
         elif info['ismagic']:
             if detail_level > 0:
                 append_field(bundle, "Source", "source", code_formatter)
             else:
                 append_field(bundle, "Docstring", "docstring", formatter)
             append_field(bundle, "File", "file")
 
         elif info['isclass'] or is_simple_callable(obj):
             # Functions, methods, classes
             append_field(bundle, "Signature", "definition", code_formatter)
             append_field(bundle, "Init signature", "init_definition", code_formatter)
             append_field(bundle, "Docstring", "docstring", formatter)
             if detail_level > 0 and info["source"]:
                 append_field(bundle, "Source", "source", code_formatter)
             else:
                 append_field(bundle, "Init docstring", "init_docstring", formatter)
 
             append_field(bundle, "File", "file")
             append_field(bundle, "Type", "type_name")
             append_field(bundle, "Subclasses", "subclasses")
 
         else:
             # General Python objects
             append_field(bundle, "Signature", "definition", code_formatter)
             append_field(bundle, "Call signature", "call_def", code_formatter)
             append_field(bundle, "Type", "type_name")
             append_field(bundle, "String form", "string_form")
 
             # Namespace
             if info["namespace"] != "Interactive":
                 append_field(bundle, "Namespace", "namespace")
 
             append_field(bundle, "Length", "length")
             append_field(bundle, "File", "file")
 
             # Source or docstring, depending on detail level and whether
             # source found.
             if detail_level > 0 and info["source"]:
                 append_field(bundle, "Source", "source", code_formatter)
             else:
                 append_field(bundle, "Docstring", "docstring", formatter)
 
             append_field(bundle, "Class docstring", "class_docstring", formatter)
             append_field(bundle, "Init docstring", "init_docstring", formatter)
             append_field(bundle, "Call docstring", "call_docstring", formatter)
         return bundle
 
 
     def _get_info(
         self,
         obj: Any,
         oname: str = "",
         formatter=None,
         info: Optional[OInfo] = None,
         detail_level=0,
         omit_sections=(),
     ) -> Bundle:
         """Retrieve an info dict and format it.
 
         Parameters
         ----------
         obj : any
             Object to inspect and return info from
         oname : str (default: ''):
             Name of the variable pointing to `obj`.
         formatter : callable
         info
             already computed information
         detail_level : integer
             Granularity of detail level, if set to 1, give more information.
         omit_sections : container[str]
             Titles or keys to omit from output (can be set, tuple, etc., anything supporting `in`)
         """
 
         info_dict = self.info(obj, oname=oname, info=info, detail_level=detail_level)
         bundle = self._make_info_unformatted(
             obj,
             info_dict,
             formatter,
             detail_level=detail_level,
             omit_sections=omit_sections,
         )
+        for key, hook in self.mime_hooks.items():
+            res = hook(obj, info)
+            if res is not None:
+                bundle[key] = res
         return self.format_mime(bundle)
 
     def pinfo(
         self,
         obj,
         oname="",
         formatter=None,
         info: Optional[OInfo] = None,
         detail_level=0,
         enable_html_pager=True,
         omit_sections=(),
     ):
         """Show detailed information about an object.
 
         Optional arguments:
 
         - oname: name of the variable pointing to the object.
 
         - formatter: callable (optional)
               A special formatter for docstrings.
 
               The formatter is a callable that takes a string as an input
               and returns either a formatted string or a mime type bundle
               in the form of a dictionary.
 
               Although the support of custom formatter returning a string
               instead of a mime type bundle is deprecated.
 
         - info: a structure with some information fields which may have been
           precomputed already.
 
         - detail_level: if set to 1, more information is given.
 
         - omit_sections: set of section keys and titles to omit
         """
         assert info is not None
         info_b: Bundle = self._get_info(
             obj, oname, formatter, info, detail_level, omit_sections=omit_sections
         )
         if not enable_html_pager:
             del info_b["text/html"]
         page.page(info_b)
 
     def _info(self, obj, oname="", info=None, detail_level=0):
         """
         Inspector.info() was likely improperly marked as deprecated
         while only a parameter was deprecated. We "un-deprecate" it.
         """
 
         warnings.warn(
             "The `Inspector.info()` method has been un-deprecated as of 8.0 "
             "and the `formatter=` keyword removed. `Inspector._info` is now "
             "an alias, and you can just call `.info()` directly.",
             DeprecationWarning,
             stacklevel=2,
         )
         return self.info(obj, oname=oname, info=info, detail_level=detail_level)
 
     def info(self, obj, oname="", info=None, detail_level=0) -> Dict[str, Any]:
         """Compute a dict with detailed information about an object.
 
         Parameters
         ----------
         obj : any
             An object to find information about
         oname : str (default: '')
             Name of the variable pointing to `obj`.
         info : (default: None)
             A struct (dict like with attr access) with some information fields
             which may have been precomputed already.
         detail_level : int (default:0)
             If set to 1, more information is given.
 
         Returns
         -------
         An object info dict with known fields from `info_fields`. Keys are
         strings, values are string or None.
         """
 
         if info is None:
             ismagic = False
             isalias = False
             ospace = ''
         else:
             ismagic = info.ismagic
             isalias = info.isalias
             ospace = info.namespace
 
         # Get docstring, special-casing aliases:
         att_name = oname.split(".")[-1]
         parents_docs = None
         prelude = ""
         if info and info.parent is not None and hasattr(info.parent, HOOK_NAME):
             parents_docs_dict = getattr(info.parent, HOOK_NAME)
             parents_docs = parents_docs_dict.get(att_name, None)
         out = dict(
             name=oname, found=True, isalias=isalias, ismagic=ismagic, subclasses=None
         )
 
         if parents_docs:
             ds = parents_docs
         elif isalias:
             if not callable(obj):
                 try:
                     ds = "Alias to the system command:\n  %s" % obj[1]
                 except:
                     ds = "Alias: " + str(obj)
             else:
                 ds = "Alias to " + str(obj)
                 if obj.__doc__:
                     ds += "\nDocstring:\n" + obj.__doc__
         else:
             ds_or_None = getdoc(obj)
             if ds_or_None is None:
                 ds = '<no docstring>'
             else:
                 ds = ds_or_None
 
         ds = prelude + ds
 
         # store output in a dict, we initialize it here and fill it as we go
 
         string_max = 200 # max size of strings to show (snipped if longer)
         shalf = int((string_max - 5) / 2)
 
         if ismagic:
             out['type_name'] = 'Magic function'
         elif isalias:
             out['type_name'] = 'System alias'
         else:
             out['type_name'] = type(obj).__name__
 
         try:
             bclass = obj.__class__
             out['base_class'] = str(bclass)
         except:
             pass
 
         # String form, but snip if too long in ? form (full in ??)
         if detail_level >= self.str_detail_level:
             try:
                 ostr = str(obj)
                 str_head = 'string_form'
                 if not detail_level and len(ostr)>string_max:
                     ostr = ostr[:shalf] + ' <...> ' + ostr[-shalf:]
                     ostr = ("\n" + " " * len(str_head.expandtabs())).\
                             join(q.strip() for q in ostr.split("\n"))
                 out[str_head] = ostr
             except:
                 pass
 
         if ospace:
             out['namespace'] = ospace
 
         # Length (for strings and lists)
         try:
             out['length'] = str(len(obj))
         except Exception:
             pass
 
         # Filename where object was defined
         binary_file = False
         fname = find_file(obj)
         if fname is None:
             # if anything goes wrong, we don't want to show source, so it's as
             # if the file was binary
             binary_file = True
         else:
             if fname.endswith(('.so', '.dll', '.pyd')):
                 binary_file = True
             elif fname.endswith('<string>'):
                 fname = 'Dynamically generated function. No source code available.'
             out['file'] = compress_user(fname)
 
         # Original source code for a callable, class or property.
         if detail_level:
             # Flush the source cache because inspect can return out-of-date
             # source
             linecache.checkcache()
             try:
                 if isinstance(obj, property) or not binary_file:
                     src = getsource(obj, oname)
                     if src is not None:
                         src = src.rstrip()
                     out['source'] = src
 
             except Exception:
                 pass
 
         # Add docstring only if no source is to be shown (avoid repetitions).
         if ds and not self._source_contains_docstring(out.get('source'), ds):
             out['docstring'] = ds
 
         # Constructor docstring for classes
         if inspect.isclass(obj):
             out['isclass'] = True
 
             # get the init signature:
             try:
                 init_def = self._getdef(obj, oname)
             except AttributeError:
                 init_def = None
 
             # get the __init__ docstring
             try:
                 obj_init = obj.__init__
             except AttributeError:
                 init_ds = None
             else:
                 if init_def is None:
                     # Get signature from init if top-level sig failed.
                     # Can happen for built-in types (list, etc.).
                     try:
                         init_def = self._getdef(obj_init, oname)
                     except AttributeError:
                         pass
                 init_ds = getdoc(obj_init)
                 # Skip Python's auto-generated docstrings
                 if init_ds == _object_init_docstring:
                     init_ds = None
 
             if init_def:
                 out['init_definition'] = init_def
 
             if init_ds:
                 out['init_docstring'] = init_ds
 
             names = [sub.__name__ for sub in type.__subclasses__(obj)]
             if len(names) < 10:
                 all_names = ', '.join(names)
             else:
                 all_names = ', '.join(names[:10]+['...'])
             out['subclasses'] = all_names
         # and class docstring for instances:
         else:
             # reconstruct the function definition and print it:
             defln = self._getdef(obj, oname)
             if defln:
                 out['definition'] = defln
 
             # First, check whether the instance docstring is identical to the
             # class one, and print it separately if they don't coincide.  In
             # most cases they will, but it's nice to print all the info for
             # objects which use instance-customized docstrings.
             if ds:
                 try:
                     cls = getattr(obj,'__class__')
                 except:
                     class_ds = None
                 else:
                     class_ds = getdoc(cls)
                 # Skip Python's auto-generated docstrings
                 if class_ds in _builtin_type_docstrings:
                     class_ds = None
                 if class_ds and ds != class_ds:
                     out['class_docstring'] = class_ds
 
             # Next, try to show constructor docstrings
             try:
                 init_ds = getdoc(obj.__init__)
                 # Skip Python's auto-generated docstrings
                 if init_ds == _object_init_docstring:
                     init_ds = None
             except AttributeError:
                 init_ds = None
             if init_ds:
                 out['init_docstring'] = init_ds
 
             # Call form docstring for callable instances
             if safe_hasattr(obj, '__call__') and not is_simple_callable(obj):
                 call_def = self._getdef(obj.__call__, oname)
                 if call_def and (call_def != out.get('definition')):
                     # it may never be the case that call def and definition differ,
                     # but don't include the same signature twice
                     out['call_def'] = call_def
                 call_ds = getdoc(obj.__call__)
                 # Skip Python's auto-generated docstrings
                 if call_ds == _func_call_docstring:
                     call_ds = None
                 if call_ds:
                     out['call_docstring'] = call_ds
 
         return object_info(**out)
 
     @staticmethod
     def _source_contains_docstring(src, doc):
         """
         Check whether the source *src* contains the docstring *doc*.
 
         This is is helper function to skip displaying the docstring if the
         source already contains it, avoiding repetition of information.
         """
         try:
             (def_node,) = ast.parse(dedent(src)).body
             return ast.get_docstring(def_node) == doc  # type: ignore[arg-type]
         except Exception:
             # The source can become invalid or even non-existent (because it
             # is re-fetched from the source file) so the above code fail in
             # arbitrary ways.
             return False
 
     def psearch(self,pattern,ns_table,ns_search=[],
                 ignore_case=False,show_all=False, *, list_types=False):
         """Search namespaces with wildcards for objects.
 
         Arguments:
 
         - pattern: string containing shell-like wildcards to use in namespace
           searches and optionally a type specification to narrow the search to
           objects of that type.
 
         - ns_table: dict of name->namespaces for search.
 
         Optional arguments:
 
           - ns_search: list of namespace names to include in search.
 
           - ignore_case(False): make the search case-insensitive.
 
           - show_all(False): show all names, including those starting with
             underscores.
 
           - list_types(False): list all available object types for object matching.
         """
         #print 'ps pattern:<%r>' % pattern # dbg
 
         # defaults
         type_pattern = 'all'
         filter = ''
 
         # list all object types
         if list_types:
             page.page('\n'.join(sorted(typestr2type)))
             return
 
         cmds = pattern.split()
         len_cmds  =  len(cmds)
         if len_cmds == 1:
             # Only filter pattern given
             filter = cmds[0]
         elif len_cmds == 2:
             # Both filter and type specified
             filter,type_pattern = cmds
         else:
             raise ValueError('invalid argument string for psearch: <%s>' %
                              pattern)
 
         # filter search namespaces
         for name in ns_search:
             if name not in ns_table:
                 raise ValueError('invalid namespace <%s>. Valid names: %s' %
                                  (name,ns_table.keys()))
 
         #print 'type_pattern:',type_pattern # dbg
         search_result, namespaces_seen = set(), set()
         for ns_name in ns_search:
             ns = ns_table[ns_name]
             # Normally, locals and globals are the same, so we just check one.
             if id(ns) in namespaces_seen:
                 continue
             namespaces_seen.add(id(ns))
             tmp_res = list_namespace(ns, type_pattern, filter,
                                     ignore_case=ignore_case, show_all=show_all)
             search_result.update(tmp_res)
 
         page.page('\n'.join(sorted(search_result)))
 
 
 def _render_signature(obj_signature, obj_name) -> str:
     """
     This was mostly taken from inspect.Signature.__str__.
     Look there for the comments.
     The only change is to add linebreaks when this gets too long.
     """
     result = []
     pos_only = False
     kw_only = True
     for param in obj_signature.parameters.values():
         if param.kind == inspect.Parameter.POSITIONAL_ONLY:
             pos_only = True
         elif pos_only:
             result.append('/')
             pos_only = False
 
         if param.kind == inspect.Parameter.VAR_POSITIONAL:
             kw_only = False
         elif param.kind == inspect.Parameter.KEYWORD_ONLY and kw_only:
             result.append('*')
             kw_only = False
 
         result.append(str(param))
 
     if pos_only:
         result.append('/')
 
     # add up name, parameters, braces (2), and commas
     if len(obj_name) + sum(len(r) + 2 for r in result) > 75:
         # This doesn’t fit behind “Signature: ” in an inspect window.
         rendered = '{}(\n{})'.format(obj_name, ''.join(
             '    {},\n'.format(r) for r in result)
         )
     else:
         rendered = '{}({})'.format(obj_name, ', '.join(result))
 
     if obj_signature.return_annotation is not inspect._empty:
         anno = inspect.formatannotation(obj_signature.return_annotation)
         rendered += ' -> {}'.format(anno)
 
     return rendered