pandoc version is now checked at each call to pandoc.pandoc(...). Version is tested with IPython.utils.version.version_check

IPython/nbconvert/utils/pandoc.py

@@ -1,142 +1,158 b''
 """Utility for calling pandoc"""
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013 the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from __future__ import print_function
 
 # Stdlib imports
 import subprocess
 import re
 import warnings
 from io import TextIOWrapper, BytesIO
 
 # IPython imports
 from IPython.utils.py3compat import cast_bytes
+from IPython.utils.version import check_version
+
 
 from .exceptions import ConversionException
 
 
 #----------------------------------------------------------------------------
 # Preliminary checks.
 # Not finding Pandoc is not always fatal so only a warning is issued at the
 # module root level so that the import of this module is not fatal. 
 #----------------------------------------------------------------------------
 
 class PandocMissing(ConversionException):
     """Exception raised when Pandoc is missing. """
     def __init__(self, cmd, exc, *args, **kwargs):
         super(PandocMissing, self).__init__( "The command '%s' returned an error: %s.\n" %(" ".join(cmd), exc) +
                                              "Please check that pandoc is installed:\n" +
                                              "http://johnmacfarlane.net/pandoc/installing.html" )
 
 def pandoc_available(failmode="return", warn=False, alt=None):
     """Is pandoc available. Only tries to call Pandoc
     and inform you that it succeeded or failed. 
     
     Parameters
     ----------
      - failmode : string
         either "return" or "raise". If "return" and pandoc
         is not available, will return (False, e) where e is
         the exception returned by subprocess.check_call.
      - warn : bool
         issue a user warning if pandoc is not available.
      - alt: list of strings
         command to print in the error (not used as actual call)
 
     Return
     ------
     out : (Bool, Exception)
         On success will return (True, None). On failure and failmode=="return" 
         will return (False, OSError instance)
     """
     
     cmd  = ["pandoc", "-v"]
 
     try:
         out = subprocess.check_output(cmd, universal_newlines=True)
         return True, None
     except OSError as e:
         if warn:
             warnings.warn(
                 "Pandoc cannot be found (calling %s failed).\n" % " ".join(alt or cmd) +
                 "Please check that pandoc is installed:\n" +
                 "http://johnmacfarlane.net/pandoc/installing.html"
             )
 
         if failmode == "return":
             return False, e
         else:
             raise PandocMissing(alt or cmd, e)
             
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 
 minimal_version = "1.12.1"
+minimal_version_ok = False
 
 def pandoc(source, fmt, to, extra_args=None, encoding='utf-8'):
     """Convert an input string in format `from` to format `to` via pandoc.
 
-    This function will raise an error if pandoc is not installed.
+    This function will raise PandocMissing if pandoc is not installed.
     Any error messages generated by pandoc are printed to stderr.
 
     Parameters
     ----------
     source : string
       Input string, assumed to be valid format `from`.
     fmt : string
       The name of the input format (markdown, etc.)
     to : string
       The name of the output format (html, etc.)
 
     Returns
     -------
     out : unicode
       Output as returned by pandoc.
     """
     cmd = ['pandoc', '-f', fmt, '-t', to]
     if extra_args:
         cmd.extend(extra_args)
 
     # if pandoc is missing let the exception bubble us out of here
     pandoc_available(failmode="raise", alt=cmd)
+    check_pandoc_version()
     
     # we can safely continue
     p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE)
     out, _ = p.communicate(cast_bytes(source, encoding))
     out = TextIOWrapper(BytesIO(out), encoding, 'replace').read()
     return out.rstrip('\n')
 
 
 def get_pandoc_version():
-    """Gets the Pandoc version if Pandoc is installed."""
+    """Gets the Pandoc version if Pandoc is installed.
+    PandocMissing will be raised if pandoc is unavailable.
+    """
     try:
-        return pandoc.version
+        if not minimal_version_ok:
+            raise AttributeError()
+        else:
+            return pandoc.version
     except AttributeError:
-        out = pandoc("None", "None", "None", ["-v"])
+        cmd = ["pandoc", "-v"]
+        try:
+            out = subprocess.check_output(cmd, universal_newlines=True)
+        except OSError as e:
+            raise PandocMissing(cmd, e)
         pv_re = re.compile(r'(\d{0,3}\.\d{0,3}\.\d{0,3})')
         pandoc.version = pv_re.search(out).group(0)
         return pandoc.version
 
 def check_pandoc_version():
-    """Returns True if minimal pandoc version is met"""
-    return get_pandoc_version() >= minimal_version
-
-if pandoc_available(warn=True)[0]:
-    if(not check_pandoc_version()):
-        warnings.warn( "You are using an old version of pandoc (%s)\n" % pandoc.version + 
-                       "Recommended version is %s.\nTry updating." % minimal_version + 
-                       "http://johnmacfarlane.net/pandoc/installing.html.\nContinuing with doubts...",
-                       RuntimeWarning, stacklevel=2)
+    """Returns True if minimal pandoc version is met.
+    PandocMissing will be raised if pandoc is unavailable.
+    """
+    global minimal_version_ok
+    if not minimal_version_ok:
+        minimal_version_ok = check_version( get_pandoc_version(), minimal_version )
+        if not minimal_version_ok:
+            warnings.warn( "You are using an old version of pandoc (%s)\n" % pandoc.version + 
+                           "Recommended version is %s.\nTry updating." % minimal_version + 
+                           "http://johnmacfarlane.net/pandoc/installing.html.\nContinuing with doubts...",
+                           RuntimeWarning, stacklevel=2)
+    return minimal_version_ok