Add a limit to the amount of files to print

codeowners_diff.py

@@ -4,7 +4,6 @@
 import difflib
 import functools
 import glob
-import operator
 import os.path
 import re
 import subprocess
@@ -69,9 +68,12 @@ def of(self, filepath: str) -> tuple[str, ...]:
 
 class MarkdownPrinter:
     def __init__(
-        self, changed_owners: Mapping[str, Mapping[str, tuple[str, ...]]],
+        self,
+        changed_owners: Mapping[str, Mapping[str, tuple[str, ...]]],
+        max_files_to_print: int | None,
     ) -> None:
         self.changed_owners = changed_owners
+        self.max_files_to_print = max_files_to_print
 
     def render_lines(self) -> Iterator[str]:
         if not self.changed_owners:
@@ -80,24 +82,38 @@ def render_lines(self) -> Iterator[str]:
 
         yield f'{len(self.changed_owners)} files have changed ownership:'
         yield ''
-        yield from tabulate(
+
+        files_to_print = list(
             sorted(
-                (
-                    {
-                        'file': f'`{file}`',
-                        **{
-                            self._column_title(ref): ', '.join(owners_)
-                            for ref, owners_ in owners.items()
-                        },
-                    }
-                    for file, owners in self.changed_owners.items()
-                ),
-                key=operator.itemgetter('file'),  # type: ignore[arg-type]
+                self.changed_owners.items(),
+            ),
+        )[:self.max_files_to_print]
+
+        yield from tabulate(
+            (
+                {
+                    'file': f'`{file}`',
+                    **{
+                        self._column_title(ref): ', '.join(owners_)
+                        for ref, owners_ in owners.items()
+                    },
+                }
+                for file, owners in files_to_print
             ),
             headers='keys',
             tablefmt='pipe',
         ).splitlines()
 
+        if (
+            self.max_files_to_print is not None and
+            (len(self.changed_owners) > self.max_files_to_print)
+        ):
+            yield ''
+            yield (
+                'Note that the above table was truncated to '
+                f'{self.max_files_to_print} items.'
+            )
+
     def _column_title(self, ref: str) -> str:
         if ref:
             return f'`{ref}`'
@@ -151,6 +167,11 @@ def main(argv: Sequence[str] | None = None) -> int:
         dest='repo_root', default=None,
         help='git repository to run the tool in (default: current directory)',
     )
+    parser.add_argument(
+        '--limit',
+        default=None,
+        help='maximum files to show in diff message (default: no limit)',
+    )
     args = parser.parse_args(argv)
 
     git_repo = GitRepo(args.repo_root)
@@ -180,7 +201,7 @@ def main(argv: Sequence[str] | None = None) -> int:
         if base_file_owners[file] != head_file_owners[file]
     }
 
-    printer = MarkdownPrinter(changed_file_owners)
+    printer = MarkdownPrinter(changed_file_owners, max_files_to_print=args.limit)
     print(*printer.render_lines(), sep='\n')
 
     return 0

tests/codeowners_diff_test.py

@@ -109,16 +109,18 @@ def test_handle_missing_codeowners_file(
 
 class TestMarkdownPrinter:
     def test_render_lines(self) -> None:
-        printer = codeowners_diff.MarkdownPrinter({
-            'foo/bar/baz.py': {
-                'base': ('@some-owner', '@some/team'),
-                'HEAD': ('@another/team',),
-            },
-            'foo/bar/bang.py': {
-                'base': ('@some/team',),
-                'HEAD': ('@another/team', '@some-user'),
-            },
-        })
+        printer = codeowners_diff.MarkdownPrinter(
+            {
+                'foo/bar/baz.py': {
+                    'base': ('@some-owner', '@some/team'),
+                    'HEAD': ('@another/team',),
+                },
+                'foo/bar/bang.py': {
+                    'base': ('@some/team',),
+                    'HEAD': ('@another/team', '@some-user'),
+                },
+            }, None,
+        )
 
         lines = printer.render_lines()
         assert '\n'.join(lines) == """\
@@ -130,7 +132,36 @@ def test_render_lines(self) -> None:
 | `foo/bar/baz.py`  | @some-owner, @some/team | @another/team             |"""
 
     def test_no_changes(self) -> None:
-        printer = codeowners_diff.MarkdownPrinter({})
+        printer = codeowners_diff.MarkdownPrinter({}, None)
 
         lines = printer.render_lines()
         assert '\n'.join(lines) == 'No files have changed ownership.'
+
+    def test_max_files_to_print(self) -> None:
+        printer = codeowners_diff.MarkdownPrinter(
+            {
+                'foo/bar/baz.py': {
+                    'base': ('@some-owner', '@some/team'),
+                    'HEAD': ('@another/team',),
+                },
+                'foo/bar/bash.py': {
+                    'base': ('@some-owner', '@some/team'),
+                    'HEAD': ('@another/team',),
+                },
+                'foo/bar/bang.py': {
+                    'base': ('@some/team',),
+                    'HEAD': ('@another/team', '@some-user'),
+                },
+            }, None,
+        )
+
+        lines = printer.render_lines()
+        assert '\n'.join(lines) == """\
+3 files have changed ownership:
+
+| file              | `base`                  | `HEAD`                    |
+|:------------------|:------------------------|:--------------------------|
+| `foo/bar/bang.py` | @some/team              | @another/team, @some-user |
+| `foo/bar/baz.py`  | @some-owner, @some/team | @another/team             |
+
+Note that the above table was truncated to 2 items."""

tests/end_to_end_test.py

@@ -80,6 +80,29 @@ def test_compare_working_tree_with_HEAD(
     assert captured.err == ''
 
 
+def test_limit_is_respected(
+        tmp_path: Path, capsys: pytest.CaptureFixture[str],
+) -> None:
+    _create_git_repo(tmp_path)
+    _create_branch(tmp_path, 'branch-a', '@some-user')
+    _create_branch(tmp_path, 'branch-b', '@another/team')
+
+    codeowners_diff.main(
+        ('branch-a', 'branch-b', '-C', str(tmp_path), '--limit', '0'),
+    )
+
+    captured = capsys.readouterr()
+    assert captured.out == """\
+1 files have changed ownership:
+
+| file             | `branch-a`   | `branch-b`    |
+|:-----------------|:-------------|:--------------|
+
+Note that the above table was truncated to 0 items.
+"""
+    assert captured.err == ''
+
+
 def _create_git_repo(root_dir: Path) -> None:
     subprocess.run(('git', 'init'), cwd=root_dir)