issue #477: explicitly populate Py2.4 linecache from Importer.

mitogen/core.py

@@ -37,6 +37,7 @@ import encodings.latin_1
 import errno
 import fcntl
 import itertools
+import linecache
 import logging
 import pickle as py_pickle
 import os
@@ -128,6 +129,7 @@ except NameError:
     BaseException = Exception
 
 IS_WSL = 'Microsoft' in os.uname()[2]
+PY24 = sys.version_info < (2, 5)
 PY3 = sys.version_info > (3,)
 if PY3:
     b = str.encode
@@ -1091,15 +1093,31 @@ class Importer(object):
         self._callbacks = {}
         self._cache = {}
         if core_src:
+            self._update_linecache('x/mitogen/core.py', core_src)
             self._cache['mitogen.core'] = (
                 'mitogen.core',
                 None,
-                'mitogen/core.py',
+                'x/mitogen/core.py',
                 zlib.compress(core_src, 9),
                 [],
             )
         self._install_handler(router)
 
+    def _update_linecache(self, path, data):
+        """
+        The Python 2.4 linecache module, used to fetch source code for
+        tracebacks and :func:`inspect.getsource`, does not support PEP-302,
+        meaning it needs extra help to for Mitogen-loaded modules. Directly
+        populate its cache if a loaded module belongs to the Mitogen package.
+        """
+        if PY24 and 'mitogen' in path:
+            linecache.cache[path] = (
+                len(data),
+                0.0,
+                data.splitlines(),
+                path,
+            )
+
     def _install_handler(self, router):
         router.add_handler(
             fn=self._on_load_module,
@@ -1214,6 +1232,11 @@ class Importer(object):
         self._lock.acquire()
         try:
             self._cache[fullname] = tup
+            if tup[2] is not None and PY24:
+                self._update_linecache(
+                    path='master:' + tup[2],
+                    data=zlib.decompress(tup[3])
+                )
             callbacks = self._callbacks.pop(fullname, [])
         finally:
             self._lock.release()