Created tool for handling interactive input blocks.

Currently it has 100% test coverage, we should try to keep it that way.

IPython/core/blockbreaker.py

@@ -0,0 +1,385 b''
+"""Analysis of text input into executable blocks.
+
+This is a simple example of how an interactive terminal-based client can use
+this tool::
+
+    bb = BlockBreaker()
+    while not bb.interactive_block_ready():
+        bb.push(raw_input('>>> '))
+    print 'Input source was:\n', bb.source,
+"""
+#-----------------------------------------------------------------------------
+#  Copyright (C) 2010  The IPython Development Team
+#
+#  Distributed under the terms of the BSD License.  The full license is in
+#  the file COPYING, distributed as part of this software.
+#-----------------------------------------------------------------------------
+
+#-----------------------------------------------------------------------------
+# Imports
+#-----------------------------------------------------------------------------
+# stdlib
+import codeop
+import re
+import sys
+
+#-----------------------------------------------------------------------------
+# Utilities
+#-----------------------------------------------------------------------------
+
+# compiled regexps for autoindent management
+dedent_re = re.compile(r'^\s+raise|^\s+return|^\s+pass')
+ini_spaces_re = re.compile(r'^([ \t\r\f\v]+)')
+
+
+def num_ini_spaces(s):
+    """Return the number of initial spaces in a string.
+
+    Note that tabs are counted as a single space.  For now, we do *not* support
+    mixing of tabs and spaces in the user's input.
+
+    Parameters
+    ----------
+    s : string
+    """
+
+    ini_spaces = ini_spaces_re.match(s)
+    if ini_spaces:
+        return ini_spaces.end()
+    else:
+        return 0
+
+
+def remove_comments(src):
+    """Remove all comments from input source.
+
+    Note: comments are NOT recognized inside of strings!
+
+    Parameters
+    ----------
+    src : string
+      A single or multiline input string.
+
+    Returns
+    -------
+    String with all Python comments removed.
+    """
+
+    return re.sub('#.*', '', src)
+
+
+def get_input_encoding():
+    """Return the default standard input encoding."""
+    return getattr(sys.stdin, 'encoding', 'ascii')
+
+#-----------------------------------------------------------------------------
+# Classes and functions
+#-----------------------------------------------------------------------------
+
+
+class BlockBreaker(object):
+    # List
+    buffer = None
+    # Command compiler
+    compile = None
+    # Number of spaces of indentation
+    indent_spaces = 0
+    # String, indicating the default input encoding
+    encoding = ''
+    # String where the current full source input is stored, properly encoded
+    source = ''
+    # Code object corresponding to the current source
+    code = None
+    # Boolean indicating whether the current block is complete
+    is_complete = None
+    
+    def __init__(self):
+        self.buffer = []
+        self.compile = codeop.CommandCompiler()
+        self.encoding = get_input_encoding()
+
+    def reset(self):
+        """Reset the input buffer and associated state."""
+        self.indent_spaces = 0
+        self.buffer[:] = []
+        self.source = ''
+
+    def get_source(self, reset=False):
+        """Return the input source.
+
+        Parameters
+        ----------
+        reset : boolean
+          If true, all state is reset and prior input forgotten.
+        """
+        out = self.source
+        if reset:
+            self.reset()
+        return out
+
+    def update_indent(self, lines):
+        """Keep track of the indent level."""
+
+        for line in remove_comments(lines).splitlines():
+            
+            if line and not line.isspace():
+                if self.code is not None:
+                    inisp = num_ini_spaces(line)
+                    if inisp < self.indent_spaces:
+                        self.indent_spaces = inisp
+
+                if line[-1] == ':':
+                    self.indent_spaces += 4
+                elif dedent_re.match(line):
+                    self.indent_spaces -= 4
+
+    def store(self, lines):
+        """Store one or more lines of input.
+
+        If input lines are not newline-terminated, a newline is automatically
+        appended."""
+
+        if lines.endswith('\n'):
+            self.buffer.append(lines)
+        else:
+            self.buffer.append(lines+'\n')
+        self.source = ''.join(self.buffer).encode(self.encoding)
+
+    def push(self, lines):
+        """Push one ore more lines of input.
+
+        This stores the given lines and returns a status code indicating
+        whether the code forms a complete Python block or not.
+
+        Any exceptions generated in compilation are allowed to propagate.
+
+        Parameters
+        ----------
+        lines : string
+          One or more lines of Python input.
+        
+        Returns
+        -------
+        is_complete : boolean
+          True if the current input source (the result of the current input
+        plus prior inputs) forms a complete Python execution block.  Note that
+        this value is also stored as an attribute so it can be queried at any
+        time.
+        """
+        # If the source code has leading blanks, add 'if 1:\n' to it
+        # this allows execution of indented pasted code. It is tempting
+        # to add '\n' at the end of source to run commands like ' a=1'
+        # directly, but this fails for more complicated scenarios
+        if not self.buffer and lines[:1] in [' ', '\t']:
+            lines = 'if 1:\n%s' % lines
+        
+        self.store(lines)
+        source = self.source
+
+        # Before calling compile(), reset the code object to None so that if an
+        # exception is raised in compilation, we don't mislead by having
+        # inconsistent code/source attributes.
+        self.code, self.is_complete = None, None
+        self.code = self.compile(source)
+        # Compilation didn't produce any exceptions (though it may not have
+        # given a complete code object)
+        if self.code is None:
+            self.is_complete = False
+        else:
+            self.is_complete = True
+        self.update_indent(lines)
+        return self.is_complete
+
+    def interactive_block_ready(self):
+        """Return whether a block of interactive input is ready for execution.
+
+        This method is meant to be used by line-oriented frontends, who need to
+        guess whether a block is complete or not based solely on prior and
+        current input lines.  The BlockBreaker considers it has a complete
+        interactive block when *all* of the following are true:
+
+        1. The input compiles to a complete statement.
+        
+        2. The indentation level is flush-left (because if we are indented,
+           like inside a function definition or for loop, we need to keep
+           reading new input).
+          
+        3. There is one extra line consisting only of whitespace.
+
+        Because of condition #3, this method should be used only by
+        *line-oriented* frontends, since it means that intermediate blank lines
+        are not allowed in function definitions (or any other indented block).
+
+        Block-oriented frontends that have a separate keyboard event to
+        indicate execution should use the :meth:`split_blocks` method instead.
+        """
+        if not self.is_complete:
+            return False
+        if self.indent_spaces==0:
+            return True
+        last_line = self.source.splitlines()[-1]
+        if not last_line or last_line.isspace():
+            return True
+        else:
+            return False
+
+
+    def split_blocks(self, lines):
+        """Split a multiline string into multiple input blocks"""
+
+#-----------------------------------------------------------------------------
+# Tests
+#-----------------------------------------------------------------------------
+
+import unittest
+
+import nose.tools as nt
+
+    
+def test_spaces():
+    tests = [('', 0),
+             (' ', 1),
+             ('\n', 0),
+             (' \n', 1),
+             ('x', 0),
+             (' x', 1),
+             ('  x',2),
+             ('    x',4),
+             # Note: tabs are counted as a single whitespace!
+             ('\tx', 1),
+             ('\t x', 2),
+             ]
+    
+    for s, nsp in tests:
+        nt.assert_equal(num_ini_spaces(s), nsp)
+
+
+def test_remove_comments():
+    tests = [('text', 'text'),
+             ('text # comment', 'text '),
+             ('text # comment\n', 'text \n'),
+             ('text # comment \n', 'text \n'),
+             ('line # c \nline\n','line \nline\n'),
+             ('line # c \nline#c2  \nline\nline #c\n\n',
+              'line \nline\nline\nline \n\n'),
+             ]
+
+    for inp, out in tests:
+        nt.assert_equal(remove_comments(inp), out)
+
+
+def test_get_input_encoding():
+    encoding = get_input_encoding()
+    nt.assert_true(isinstance(encoding, basestring))
+    # simple-minded check that at least encoding a simple string works with the
+    # encoding we got.
+    nt.assert_equal('test'.encode(encoding), 'test')
+
+
+class BlockBreakerTestCase(unittest.TestCase):
+    def setUp(self):
+        self.bb = BlockBreaker()
+
+    def test_reset(self):
+        self.bb.store('hello')
+        self.bb.reset()
+        self.assertEqual(self.bb.buffer, [])
+        self.assertEqual(self.bb.indent_spaces, 0)
+        self.assertEqual(self.bb.get_source(), '')
+
+    def test_source(self):
+        self.bb.store('1')
+        self.bb.store('2')
+        out = self.bb.get_source()
+        self.assertEqual(out, '1\n2\n')
+        out = self.bb.get_source(reset=True)
+        self.assertEqual(out, '1\n2\n')
+        self.assertEqual(self.bb.buffer, [])
+        out = self.bb.get_source()
+        self.assertEqual(out, '')
+        
+    def test_indent(self):
+        bb = self.bb # shorthand
+        bb.push('x=1')
+        self.assertEqual(bb.indent_spaces, 0)
+        bb.push('if 1:\n    x=1')
+        self.assertEqual(bb.indent_spaces, 4)
+        bb.push('y=2\n')
+        self.assertEqual(bb.indent_spaces, 0)
+        bb.push('if 1:')
+        self.assertEqual(bb.indent_spaces, 4)
+        bb.push('    x=1')
+        self.assertEqual(bb.indent_spaces, 4)
+        # Blank lines shouldn't change the indent level
+        bb.push(' '*2)
+        self.assertEqual(bb.indent_spaces, 4)
+
+    def test_indent2(self):
+        bb = self.bb
+        # When a multiline statement contains parens or multiline strings, we
+        # shouldn't get confused.
+        bb.push("if 1:")
+        bb.push("    x = (1+\n    2)")
+        self.assertEqual(bb.indent_spaces, 4)
+
+    def test_dedent(self):
+        bb = self.bb # shorthand
+        bb.push('if 1:')
+        self.assertEqual(bb.indent_spaces, 4)
+        bb.push('    pass')
+        self.assertEqual(bb.indent_spaces, 0)
+        
+    def test_push(self):
+        bb = self.bb
+        bb.push('x=1')
+        self.assertTrue(bb.is_complete)
+
+    def test_push2(self):
+        bb = self.bb
+        bb.push('if 1:')
+        self.assertFalse(bb.is_complete)
+        for line in ['  x=1', '# a comment', '  y=2']:
+            bb.push(line)
+            self.assertTrue(bb.is_complete)
+            
+    def test_push3(self):
+        """Test input with leading whitespace"""
+        bb = self.bb
+        bb.push('  x=1')
+        bb.push('  y=2')
+        self.assertEqual(bb.source, 'if 1:\n  x=1\n  y=2\n')
+
+    def test_interactive_block_ready(self):
+        bb = self.bb
+        bb.push('x=1')
+        self.assertTrue(bb.interactive_block_ready())
+
+    def test_interactive_block_ready2(self):
+        bb = self.bb
+        bb.push('if 1:\n  x=1')
+        self.assertFalse(bb.interactive_block_ready())
+        bb.push('')
+        self.assertTrue(bb.interactive_block_ready())
+        
+    def test_interactive_block_ready3(self):
+        bb = self.bb
+        bb.push("x = (2+\n3)")
+        self.assertTrue(bb.interactive_block_ready())
+
+    def test_interactive_block_ready4(self):
+        bb = self.bb
+        # When a multiline statement contains parens or multiline strings, we
+        # shouldn't get confused.
+        # FIXME: we should be able to better handle de-dents in statements like
+        # multiline strings and multiline expressions (continued with \ or
+        # parens).  Right now we aren't handling the indentation tracking quite
+        # correctly with this, though in practice it may not be too much of a
+        # problem.  We'll need to see.
+        bb.push("if 1:")
+        bb.push("    x = (2+")
+        bb.push("    3)")
+        self.assertFalse(bb.interactive_block_ready())
+        bb.push("    y = 3")
+        self.assertFalse(bb.interactive_block_ready())
+        bb.push('')
+        self.assertTrue(bb.interactive_block_ready())