[Backport maintenance/3.0.x] Fixes duplicate-code check with ignore-imports

doc/whatsnew/fragments/8914.bugfix

@@ -0,0 +1,3 @@
+Fixes ignoring conditional imports with ``ignore-imports=y``.
+
+Closes #8914

pylint/checkers/similar.py

@@ -41,7 +41,7 @@
 from collections.abc import Callable, Generator, Iterable, Sequence
 from getopt import getopt
 from io import BufferedIOBase, BufferedReader, BytesIO
-from itertools import chain, groupby
+from itertools import chain
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -598,17 +598,10 @@ def stripped_lines(
     if ignore_imports or ignore_signatures:
         tree = astroid.parse("".join(lines))
     if ignore_imports:
-        node_is_import_by_lineno = (
-            (node.lineno, isinstance(node, (nodes.Import, nodes.ImportFrom)))
-            for node in tree.body
-        )
-        line_begins_import = {
-            lineno: all(is_import for _, is_import in node_is_import_group)
-            for lineno, node_is_import_group in groupby(
-                node_is_import_by_lineno, key=lambda x: x[0]
-            )
-        }
-        current_line_is_import = False
+        import_lines = {}
+        for node in tree.nodes_of_class((nodes.Import, nodes.ImportFrom)):
+            for lineno in range(node.lineno, (node.end_lineno or node.lineno) + 1):
+                import_lines[lineno] = True
     if ignore_signatures:
 
         def _get_functions(
@@ -664,9 +657,7 @@ def _get_functions(
                     docstring = None
                 line = ""
         if ignore_imports:
-            current_line_is_import = line_begins_import.get(
-                lineno, current_line_is_import
-            )
+            current_line_is_import = import_lines.get(lineno, False)
             if current_line_is_import:
                 line = ""
         if ignore_comments:

tests/checkers/unittest_similar.py

@@ -9,6 +9,7 @@
 import pytest
 
 from pylint.checkers import similar
+from pylint.constants import IS_PYPY, PY39_PLUS
 from pylint.lint import PyLinter
 from pylint.testutils import GenericTestReporter as Reporter
 
@@ -130,6 +131,10 @@ def test_multiline_imports() -> None:
     )
 
 
+@pytest.mark.skipif(
+    IS_PYPY and not PY39_PLUS,
+    reason="Requires accurate 'end_lineno' value",
+)
 def test_ignore_multiline_imports() -> None:
     output = StringIO()
     with redirect_stdout(output), pytest.raises(SystemExit) as ex:
@@ -295,7 +300,7 @@ def test_no_hide_code_with_imports() -> None:
     with redirect_stdout(output), pytest.raises(SystemExit) as ex:
         similar.Run(["--ignore-imports"] + 2 * [HIDE_CODE_WITH_IMPORTS])
     assert ex.value.code == 0
-    assert "TOTAL lines=32 duplicates=16 percent=50.00" in output.getvalue()
+    assert "TOTAL lines=32 duplicates=0 percent=0.00" in output.getvalue()
 
 
 def test_ignore_nothing() -> None:

tests/regrtest_data/duplicate_code/ignore_conditional_imports/file_one.py

@@ -0,0 +1,6 @@
+import typing
+
+x = 1
+if typing.TYPE_CHECKING:
+    import os
+    import sys

tests/regrtest_data/duplicate_code/ignore_conditional_imports/file_two.py

@@ -0,0 +1,6 @@
+import typing
+
+x = 1
+if typing.TYPE_CHECKING:
+    import os
+    import sys

tests/test_similar.py

@@ -264,3 +264,18 @@ def test_useless_suppression() -> None:
             exit=False,
         )
         assert not runner.linter.stats.by_msg
+
+    def test_conditional_imports(self) -> None:
+        """Tests enabling ignore-imports with conditional imports works correctly."""
+        path = join(DATA, "ignore_conditional_imports")
+        expected_output = "==ignore_conditional_imports.file_one:[2:4]"
+        self._test_output(
+            [
+                path,
+                "-e=duplicate-code",
+                "-d=unused-import,C",
+                "--ignore-imports=y",
+                "--min-similarity-lines=1",
+            ],
+            expected_output=expected_output,
+        )