From cd7ee80354297ce53dc505ebf6f0f1d033b4638b Mon Sep 17 00:00:00 2001
From: vitali87 <eheva87@gmail.com>
Date: Sun, 30 Aug 2026 14:03:36 +0100
Subject: [PATCH] fix: reject mode-only changes instead of silently dropping
 them

A chmod-only change produces a diff entry with no hunks. Like binary
files, nothing in the plan can claim it, coverage validation passes,
and the mode change is missing from every sub-PR. Reject it up front
with the same kind of message as binary files.
---
 pr_split/exceptions.py        |  4 ++++
 pr_split/planner/validator.py | 13 +++++++++----
 tests/test_validator.py       | 26 ++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/pr_split/exceptions.py b/pr_split/exceptions.py
index 7e9b242..7eb6529 100644
--- a/pr_split/exceptions.py
+++ b/pr_split/exceptions.py
@@ -31,6 +31,10 @@ class ErrorMsg(StrEnum):
         "Diff contains binary files, which cannot be split into hunks: {files}."
         " Commit them separately and re-run"
     )
+    HUNKLESS_FILES_UNSUPPORTED = (
+        "Diff contains files with no text hunks (mode-only or empty changes), which"
+        " cannot be assigned to a sub-PR: {files}. Commit them separately and re-run"
+    )
 
     def __call__(self, **kwargs: object) -> str:
         return self.value.format(**kwargs) if kwargs else self.value
diff --git a/pr_split/planner/validator.py b/pr_split/planner/validator.py
index 9cbe0c2..1bc5e13 100644
--- a/pr_split/planner/validator.py
+++ b/pr_split/planner/validator.py
@@ -10,15 +10,20 @@
 
 
 def validate_no_binary_files(parsed_diff: ParsedDiff) -> None:
-    """Refuse diffs with binary files.
+    """Refuse diffs with binary files or hunk-less entries.
 
-    Binary patches carry no hunks, so coverage validation would pass
-    without any group claiming them and the change would silently be
-    dropped from every sub-PR.
+    Binary patches and mode-only changes carry no hunks, so coverage
+    validation would pass without any group claiming them and the change
+    would silently be dropped from every sub-PR.
     """
     binary = [pf.path for pf in parsed_diff.patch_set if pf.is_binary_file]
     if binary:
         raise PlanValidationError(ErrorMsg.BINARY_FILES_UNSUPPORTED(files=", ".join(binary)))
+    # Mode-only changes (chmod +x) and other hunk-less entries have the same
+    # failure mode: nothing for a group to claim, so the change vanishes.
+    hunkless = [pf.path for pf in parsed_diff.patch_set if len(pf) == 0]
+    if hunkless:
+        raise PlanValidationError(ErrorMsg.HUNKLESS_FILES_UNSUPPORTED(files=", ".join(hunkless)))
 
 
 def validate_coverage(groups: list[Group], parsed_diff: ParsedDiff) -> None:
diff --git a/tests/test_validator.py b/tests/test_validator.py
index 134dca0..bfb53a9 100644
--- a/tests/test_validator.py
+++ b/tests/test_validator.py
@@ -226,3 +226,29 @@ def test_whole_file_overlapping_same_file_partial_raises(self) -> None:
         ]
         with pytest.raises(PlanValidationError, match="multiple groups"):
             validate_coverage(groups, parsed)
+
+
+MODE_ONLY_DIFF = """\
+diff --git a/run.sh b/run.sh
+old mode 100644
+new mode 100755
+diff --git a/a.py b/a.py
+--- a/a.py
++++ b/a.py
+@@ -1 +1 @@
+-x
++y
+"""
+
+
+class TestValidateNoHunklessFiles:
+    def test_mode_only_change_raises(self) -> None:
+        parsed = parse_diff(MODE_ONLY_DIFF)
+        with pytest.raises(PlanValidationError, match=r"no text hunks.*run\.sh"):
+            validate_no_binary_files(parsed)
+
+    def test_validate_plan_rejects_mode_only_even_when_text_hunks_are_covered(self) -> None:
+        parsed = parse_diff(MODE_ONLY_DIFF)
+        groups = [_make_group("g1", [_ga("a.py", WHOLE, [0])], 2)]
+        with pytest.raises(PlanValidationError, match="no text hunks"):
+            validate_plan(groups, parsed, PlanDAG(groups), max_loc=400)