allow "fake" filenames in findsource (closes #9284)

This allows findsource() to work in doctests.

A patch from Dirkjan Ochtman.

Lib/inspect.py

@@ -518,9 +518,13 @@ def findsource(object):
     or code object.  The source code is returned as a list of all the lines
     in the file and the line number indexes a line in that list.  An IOError
     is raised if the source code cannot be retrieved."""
-    file = getsourcefile(object)
-    if not file:
+
+    file = getfile(object)
+    sourcefile = getsourcefile(object)
+    if not sourcefile and file[0] + file[-1] != '<>':
         raise IOError('source code not available')
+    file = sourcefile if sourcefile else file
+
     module = getmodule(object, file)
     if module:
         lines = linecache.getlines(file, module.__dict__)

Lib/test/test_inspect.py

@@ -298,6 +298,23 @@ class TestRetrievingSourceCode(GetSourceBase):
         del sys.modules[name]
         inspect.getmodule(compile('a=10','','single'))
 
+    def test_proceed_with_fake_filename(self):
+        '''doctest monkeypatches linecache to enable inspection'''
+        fn, source = '<test>', 'def x(): pass\n'
+        getlines = linecache.getlines
+        def monkey(filename, module_globals=None):
+            if filename == fn:
+                return source.splitlines(True)
+            else:
+                return getlines(filename, module_globals)
+        linecache.getlines = monkey
+        try:
+            ns = {}
+            exec(compile(source, fn, 'single'), ns)
+            inspect.getsource(ns["x"])
+        finally:
+            linecache.getlines = getlines
+
 class TestDecorators(GetSourceBase):
     fodderModule = mod2
 

Misc/NEWS

@@ -22,6 +22,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #9284: Allow inspect.findsource() to find the source of doctest
+  functions.
+
 - Issue #12009: Fixed regression in netrc file comment handling.
 
 - Issue #10694: zipfile now ignores garbage at the end of a zipfile.