Merge pull request #2574 from apoorvdarshan/fix-isort-skip-with-future-import-2092

Honor `# isort: skip` when a __future__ import is present (#2092)

Author: DanielNoord

isort/core.py

@@ -30,6 +30,12 @@
     "# isort: assignments",
 )
 LITERAL_TYPE_MAPPING = {"(": "tuple", "[": "list", "{": "set"}
+SKIP_IMPORT_COMMENTS = ("isort:skip", "isort: skip")
+
+
+def _has_skip_comment(import_statement: str) -> bool:
+    """Return whether an import statement carries a per-line ``isort: skip`` directive."""
+    return any(comment in import_statement for comment in SKIP_IMPORT_COMMENTS)
 
 
 # Ignore DeepSource cyclomatic complexity check for this function.
@@ -325,10 +331,17 @@ def process(
                                 stripped_line = line.strip().split("#")[0]
                                 import_statement += line
 
+                    # The second clause keeps a per-line ``isort: skip`` import exactly
+                    # where it is: when earlier imports have already been collected into
+                    # the current section, the skipped statement is treated as a section
+                    # boundary so those imports can't be sorted above it.  Without it, a
+                    # preceding import (most commonly a ``__future__`` import, which is
+                    # always floated to the top) makes isort splice the sorted block
+                    # ahead of the skipped line and relocate it below the block. See #2092.
                     if (
                         import_statement.lstrip().startswith("from")
                         and "import" not in import_statement
-                    ):
+                    ) or (contains_imports and _has_skip_comment(import_statement)):
                         line = import_statement
                         not_imports = True
                     else:

tests/unit/test_regressions.py

@@ -2260,3 +2260,32 @@ def test_noqa_added_to_long_combined_straight_imports_with_bare_comment_issue_20
         to_sort, multi_line_output=7, combine_straight_imports=True, line_length=40
     )
     assert first_pass == ("import a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p  #  # NOQA\n")
+
+
+def test_isort_skip_is_honored_with_future_import_issue_2092():
+    """A per-line ``isort: skip`` must be honored even when a ``__future__`` import is present.
+
+    ``__future__`` imports are always floated to the very top, which used to make isort splice
+    the sorted import block ahead of a following ``# isort: skip`` line and relocate the skipped
+    import below the block - silently violating the skip directive.  The skipped import must stay
+    exactly where it is, and the result must be stable across re-runs.  See issue #2092.
+    """
+    to_sort = (
+        "from __future__ import annotations\n"
+        "\n"
+        "from foo import bar  # isort: skip\n"
+        "from bar import baz\n"
+    )
+
+    first_pass = isort.code(to_sort)
+    assert first_pass == to_sort
+    assert isort.check_code(to_sort, show_diff=True)
+
+    # An interleaved skip (between two regular imports) must keep its position rather than
+    # being sorted to the bottom of the block, and must be idempotent.
+    interleaved = "import aaa\nfrom foo import bar  # isort: skip\nimport ccc\n"
+    sorted_interleaved = isort.code(interleaved)
+    lines = sorted_interleaved.splitlines()
+    skip_index = next(i for i, line in enumerate(lines) if "# isort: skip" in line)
+    assert lines.index("import ccc") > skip_index  # skip not relocated below the block
+    assert isort.code(sorted_interleaved) == sorted_interleaved