Fix inspect.getsource returning truncated source for multi-line function definitions (#7519)

* Initial plan

* fix: restore def-line source range before entering function scope so co_firstlineno is correct

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* fix: remove pre-existing expectedFailure decorators from test_gettext plural form tests

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* remove extra_tests/snippets/inspect_getsource.py (covered by test_inspect)

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---------

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Lib/test/test_gettext.py

@@ -385,7 +385,6 @@ class PluralFormsTests:
                 x = ngettext(singular, plural, None)
             self.assertEqual(x, tplural)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_forms(self):
         self._test_plural_forms(
             self.ngettext, self.gettext,
@@ -396,7 +395,6 @@ class PluralFormsTests:
             '%d file deleted', '%d files deleted',
             '%d file deleted', '%d files deleted')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_context_forms(self):
         ngettext = partial(self.npgettext, 'With context')
         gettext = partial(self.pgettext, 'With context')
@@ -409,7 +407,6 @@ class PluralFormsTests:
             '%d file deleted', '%d files deleted',
             '%d file deleted', '%d files deleted')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_wrong_context_forms(self):
         self._test_plural_forms(
             partial(self.npgettext, 'Unknown context'),
@@ -442,7 +439,6 @@ class GNUTranslationsWithDomainPluralFormsTestCase(PluralFormsTests, GettextBase
         self.pgettext = partial(gettext.dpgettext, 'gettext')
         self.npgettext = partial(gettext.dnpgettext, 'gettext')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_forms_wrong_domain(self):
         self._test_plural_forms(
             partial(gettext.dngettext, 'unknown'),
@@ -451,7 +447,6 @@ class GNUTranslationsWithDomainPluralFormsTestCase(PluralFormsTests, GettextBase
             'There is %s file', 'There are %s files',
             numbers_only=False)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_context_forms_wrong_domain(self):
         self._test_plural_forms(
             partial(gettext.dnpgettext, 'unknown', 'With context'),
@@ -472,7 +467,6 @@ class GNUTranslationsClassPluralFormsTestCase(PluralFormsTests, GettextBaseTest)
         self.pgettext = t.pgettext
         self.npgettext = t.npgettext
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_forms_null_translations(self):
         t = gettext.NullTranslations()
         self._test_plural_forms(
@@ -481,7 +475,6 @@ class GNUTranslationsClassPluralFormsTestCase(PluralFormsTests, GettextBaseTest)
             'There is %s file', 'There are %s files',
             numbers_only=False)
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_plural_context_forms_null_translations(self):
         t = gettext.NullTranslations()
         self._test_plural_forms(

Lib/test/test_inspect/test_inspect.py

@@ -961,7 +961,6 @@ class TestGettingSourceOfToplevelFrames(GetSourceBase):
 class TestDecorators(GetSourceBase):
     fodderModule = mod2
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; pass
     def test_wrapped_decorator(self):
         self.assertSourceEqual(mod2.wrapped, 14, 17)
 
@@ -1259,7 +1258,6 @@ class TestNoEOL(GetSourceBase):
 class TestComplexDecorator(GetSourceBase):
     fodderModule = mod2
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; return foo + bar()
     def test_parens_in_decorator(self):
         self.assertSourceEqual(self.fodderModule.complex_decorated, 273, 275)
 

crates/codegen/src/compile.rs

@@ -4246,11 +4246,19 @@ impl Compiler {
         is_async: bool,
         type_params: Option<&ast::TypeParams>,
     ) -> CompileResult<()> {
+        // Save the source range of the `def` line before compiling decorators/defaults,
+        // so that the function code object gets the correct co_firstlineno.
+        let def_source_range = self.current_source_range;
+
         self.prepare_decorators(decorator_list)?;
 
         // compile defaults and return funcflags
         let funcflags = self.compile_default_arguments(parameters)?;
 
+        // Restore the `def` line range so that enter_function → push_output → get_source_line_number()
+        // records the `def` keyword's line as co_firstlineno, not the last default-argument line.
+        self.set_source_range(def_source_range);
+
         let is_generic = type_params.is_some();
         let mut num_typeparam_args = 0;