A fiddled version of the rest of Michael Hudson's SF patch

#449043 supporting __future__ in simulated shells
which implements PEP 264.

Lib/codeop.py

@@ -1,49 +1,69 @@
-"""Utility to compile possibly incomplete Python source code."""
+r"""Utilities to compile possibly incomplete Python source code.
 
-__all__ = ["compile_command"]
+This module provides two interfaces, broadly similar to the builtin
+function compile(), that take progam text, a filename and a 'mode'
+and:
 
-def compile_command(source, filename="<input>", symbol="single"):
-    r"""Compile a command and determine whether it is incomplete.
+- Return a code object if the command is complete and valid
+- Return None if the command is incomplete
+- Raise SyntaxError, ValueError or OverflowError if the command is a
+  syntax error (OverflowError and ValueError can be produced by
+  malformed literals).
 
-    Arguments:
+Approach:
 
-    source -- the source string; may contain \n characters
-    filename -- optional filename from which source was read; default "<input>"
-    symbol -- optional grammar start symbol; "single" (default) or "eval"
+First, check if the source consists entirely of blank lines and
+comments; if so, replace it with 'pass', because the built-in
+parser doesn't always do the right thing for these.
 
-    Return value / exceptions raised:
+Compile three times: as is, with \n, and with \n\n appended.  If it
+compiles as is, it's complete.  If it compiles with one \n appended,
+we expect more.  If it doesn't compile either way, we compare the
+error we get when compiling with \n or \n\n appended.  If the errors
+are the same, the code is broken.  But if the errors are different, we
+expect more.  Not intuitive; not even guaranteed to hold in future
+releases; but this matches the compiler's behavior from Python 1.4
+through 2.2, at least.
 
-    - Return a code object if the command is complete and valid
-    - Return None if the command is incomplete
-    - Raise SyntaxError or OverflowError if the command is a syntax error
-      (OverflowError if the error is in a numeric constant)
+Caveat:
 
-    Approach:
+It is possible (but not likely) that the parser stops parsing with a
+successful outcome before reaching the end of the source; in this
+case, trailing symbols may be ignored instead of causing an error.
+For example, a backslash followed by two newlines may be followed by
+arbitrary garbage.  This will be fixed once the API for the parser is
+better.
 
-    First, check if the source consists entirely of blank lines and
-    comments; if so, replace it with 'pass', because the built-in
-    parser doesn't always do the right thing for these.
+The two interfaces are:
 
-    Compile three times: as is, with \n, and with \n\n appended.  If
-    it compiles as is, it's complete.  If it compiles with one \n
-    appended, we expect more.  If it doesn't compile either way, we
-    compare the error we get when compiling with \n or \n\n appended.
-    If the errors are the same, the code is broken.  But if the errors
-    are different, we expect more.  Not intuitive; not even guaranteed
-    to hold in future releases; but this matches the compiler's
-    behavior from Python 1.4 through 1.5.2, at least.
+compile_command(source, filename, symbol):
 
-    Caveat:
+    Compiles a single command in the manner described above.
 
-    It is possible (but not likely) that the parser stops parsing
-    with a successful outcome before reaching the end of the source;
-    in this case, trailing symbols may be ignored instead of causing an
-    error.  For example, a backslash followed by two newlines may be
-    followed by arbitrary garbage.  This will be fixed once the API
-    for the parser is better.
+CommandCompiler():
 
-    """
+    Instances of this class have __call__ methods identical in
+    signature to compile_command; the difference is that if the
+    instance compiles program text containing a __future__ statement,
+    the instance 'remembers' and compiles all subsequent program texts
+    with the statement in force.
 
+The module also provides another class:
+
+Compile():
+
+    Instances of this class act like the built-in function compile,
+    but with 'memory' in the sense described above.
+"""
+
+import __future__
+
+_features = [getattr(__future__, fname)
+             for fname in __future__.all_feature_names]
+
+__all__ = ["compile_command", "Compile", "CommandCompiler"]
+
+def _maybe_compile(compiler, source, filename, symbol):
     # Check for source consisting of only blank lines and comments
     for line in source.split("\n"):
         line = line.strip()
@@ -56,17 +76,17 @@ def compile_command(source, filename="<input>", symbol="single"):
     code = code1 = code2 = None
 
     try:
-        code = compile(source, filename, symbol)
+        code = compiler(source, filename, symbol)
     except SyntaxError, err:
         pass
 
     try:
-        code1 = compile(source + "\n", filename, symbol)
+        code1 = compiler(source + "\n", filename, symbol)
     except SyntaxError, err1:
         pass
 
     try:
-        code2 = compile(source + "\n\n", filename, symbol)
+        code2 = compiler(source + "\n\n", filename, symbol)
     except SyntaxError, err2:
         pass
 
@@ -82,3 +102,69 @@ def compile_command(source, filename="<input>", symbol="single"):
         e2 = err2
     if not code1 and e1 == e2:
         raise SyntaxError, err1
+
+def compile_command(source, filename="<input>", symbol="single"):
+    r"""Compile a command and determine whether it is incomplete.
+
+    Arguments:
+
+    source -- the source string; may contain \n characters
+    filename -- optional filename from which source was read; default
+                "<input>"
+    symbol -- optional grammar start symbol; "single" (default) or "eval"
+
+    Return value / exceptions raised:
+
+    - Return a code object if the command is complete and valid
+    - Return None if the command is incomplete
+    - Raise SyntaxError, ValueError or OverflowError if the command is a
+      syntax error (OverflowError and ValueError can be produced by
+      malformed literals).
+    """
+    return _maybe_compile(compile, source, filename, symbol)
+
+class Compile:
+    """Instances of this class behave much like the built-in compile
+    function, but if one is used to compile text containing a future
+    statement, it "remembers" and compiles all subsequent program texts
+    with the statement in force."""
+    def __init__(self):
+        self.flags = 0
+
+    def __call__(self, source, filename, symbol):
+        codeob = compile(source, filename, symbol, self.flags, 1)
+        for feature in _features:
+            if codeob.co_flags & feature.compiler_flag:
+                self.flags |= feature.compiler_flag
+        return codeob
+
+class CommandCompiler:
+    """Instances of this class have __call__ methods identical in
+    signature to compile_command; the difference is that if the
+    instance compiles program text containing a __future__ statement,
+    the instance 'remembers' and compiles all subsequent program texts
+    with the statement in force."""
+
+    def __init__(self,):
+        self.compiler = Compile()
+
+    def __call__(self, source, filename="<input>", symbol="single"):
+        r"""Compile a command and determine whether it is incomplete.
+
+        Arguments:
+
+        source -- the source string; may contain \n characters
+        filename -- optional filename from which source was read;
+                    default "<input>"
+        symbol -- optional grammar start symbol; "single" (default) or
+                  "eval"
+
+        Return value / exceptions raised:
+
+        - Return a code object if the command is complete and valid
+        - Return None if the command is incomplete
+        - Raise SyntaxError, ValueError or OverflowError if the command is a
+          syntax error (OverflowError and ValueError can be produced by
+          malformed literals).
+        """
+        return _maybe_compile(self.compiler, source, filename, symbol)