[3.12] gh-86291: linecache: get module name from __spec__ if available (GH-22908) (GH-115731)

This allows getting source code for the __main__ module when a custom
loader is used.
(cherry picked from commit e976baba99a5c243ff3a3b5ef2fd14608a398338)

Co-authored-by: Eugene Toder <eltoder@users.noreply.github.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/Lib/test/test_linecache.py b/Lib/test/test_linecache.py
index 72dd401..e42df3d 100644
--- a/Lib/test/test_linecache.py
+++ b/Lib/test/test_linecache.py
@@ -5,6 +5,7 @@ import unittest
 import os.path
 import tempfile
 import tokenize
+from importlib.machinery import ModuleSpec
 from test import support
 from test.support import os_helper
 
@@ -97,6 +98,16 @@ class BadUnicode_WithDeclaration(GetLineTestsBadData, unittest.TestCase):
     file_byte_string = b'# coding=utf-8\n\x80abc'
 
 
+class FakeLoader:
+    def get_source(self, fullname):
+        return f'source for {fullname}'
+
+
+class NoSourceLoader:
+    def get_source(self, fullname):
+        return None
+
+
 class LineCacheTests(unittest.TestCase):
 
     def test_getline(self):
@@ -238,6 +249,33 @@ class LineCacheTests(unittest.TestCase):
         self.assertEqual(lines3, [])
         self.assertEqual(linecache.getlines(FILENAME), lines)
 
+    def test_loader(self):
+        filename = 'scheme://path'
+
+        for loader in (None, object(), NoSourceLoader()):
+            linecache.clearcache()
+            module_globals = {'__name__': 'a.b.c', '__loader__': loader}
+            self.assertEqual(linecache.getlines(filename, module_globals), [])
+
+        linecache.clearcache()
+        module_globals = {'__name__': 'a.b.c', '__loader__': FakeLoader()}
+        self.assertEqual(linecache.getlines(filename, module_globals),
+                         ['source for a.b.c\n'])
+
+        for spec in (None, object(), ModuleSpec('', FakeLoader())):
+            linecache.clearcache()
+            module_globals = {'__name__': 'a.b.c', '__loader__': FakeLoader(),
+                              '__spec__': spec}
+            self.assertEqual(linecache.getlines(filename, module_globals),
+                             ['source for a.b.c\n'])
+
+        linecache.clearcache()
+        spec = ModuleSpec('x.y.z', FakeLoader())
+        module_globals = {'__name__': 'a.b.c', '__loader__': spec.loader,
+                          '__spec__': spec}
+        self.assertEqual(linecache.getlines(filename, module_globals),
+                         ['source for x.y.z\n'])
+
 
 class LineCacheInvalidationTests(unittest.TestCase):
     def setUp(self):