implements unmeasured-as-uncovered

aweidner · aweidner · commit b47f89dca6a4 · 2026-02-20T19:31:34.000Z
diff --git a/diff_cover/diff_cover_tool.py b/diff_cover/diff_cover_tool.py
@@ -54,6 +54,9 @@
 TOTAL_PERCENT_FLOAT_HELP = (
     "Show total coverage/quality as a float rounded to 2 decimal places"
 )
+TREAT_UNMEASURED_AS_UNCOVERED_HELP = (
+    "Treat lines in the diff that are absent from the coverage report as uncovered"
+)
 
 LOGGER = logging.getLogger(__name__)
 
@@ -190,6 +193,12 @@ def parse_coverage_args(argv):
         default=None,
         help=TOTAL_PERCENT_FLOAT_HELP,
     )
+    parser.add_argument(
+        "--treat-unmeasured-as-uncovered",
+        action="store_true",
+        default=None,
+        help=TREAT_UNMEASURED_AS_UNCOVERED_HELP,
+    )
 
     defaults = {
         "show_uncovered": False,
@@ -204,6 +213,7 @@ def parse_coverage_args(argv):
         "quiet": False,
         "expand_coverage_report": False,
         "total_percent_float": False,
+        "treat_unmeasured_as_uncovered": False,
     }
 
     return get_config(parser=parser, argv=argv, defaults=defaults, tool=Tool.DIFF_COVER)
@@ -225,6 +235,7 @@ def generate_coverage_report(
     show_uncovered=False,
     expand_coverage_report=False,
     total_percent_float=False,
+    treat_unmeasured_as_uncovered=False,
 ):
     """
     Generate the diff coverage report, using kwargs from `parse_args()`.
@@ -263,7 +274,11 @@ def generate_coverage_report(
         if css_url is not None:
             css_url = os.path.relpath(css_file, os.path.dirname(html_report))
         reporter = HtmlReportGenerator(
-            coverage, diff, css_url=css_url, total_percent_float=total_percent_float
+            coverage,
+            diff,
+            css_url=css_url,
+            total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         with open_file(html_report, "wb") as output_file:
             reporter.generate_report(output_file)
@@ -274,15 +289,21 @@ def generate_coverage_report(
     if "json" in report_formats:
         json_report = report_formats["json"] or JSON_REPORT_DEFAULT_PATH
         reporter = JsonReportGenerator(
-            coverage, diff, total_percent_float=total_percent_float
+            coverage,
+            diff,
+            total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         with open_file(json_report, "wb") as output_file:
             reporter.generate_report(output_file)
 
     if "markdown" in report_formats:
         markdown_report = report_formats["markdown"] or MARKDOWN_REPORT_DEFAULT_PATH
         reporter = MarkdownReportGenerator(
-            coverage, diff, total_percent_float=total_percent_float
+            coverage,
+            diff,
+            total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         with open_file(markdown_report, "wb") as output_file:
             reporter.generate_report(output_file)
@@ -294,6 +315,7 @@ def generate_coverage_report(
             diff,
             report_formats["github-annotations"],
             total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         reporter.generate_report(sys.stdout.buffer)
 
@@ -303,6 +325,7 @@ def generate_coverage_report(
         diff,
         show_uncovered,
         total_percent_float=total_percent_float,
+        treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
     )
     output_file = io.BytesIO() if quiet else sys.stdout.buffer
 
@@ -400,6 +423,7 @@ def main(argv=None, directory=None):
         show_uncovered=arg_dict["show_uncovered"],
         expand_coverage_report=arg_dict["expand_coverage_report"],
         total_percent_float=arg_dict["total_percent_float"],
+        treat_unmeasured_as_uncovered=arg_dict["treat_unmeasured_as_uncovered"],
     )
 
     if percent_covered >= fail_under:
diff --git a/diff_cover/diff_reporter.py b/diff_cover/diff_reporter.py
@@ -399,8 +399,10 @@ def _parse_lines(self, diff_lines):
                 # calling this method, we're guaranteed to have a source
                 # file specified.  We check anyway just to be safe.
                 if current_line_new is not None:
-                    # Store the added line
-                    added_lines.append(current_line_new)
+                    # Skip blank/whitespace-only added lines
+                    if line[1:].strip():
+                        # Store the added line
+                        added_lines.append(current_line_new)
 
                     # Increment the line number in the file
                     current_line_new += 1
diff --git a/diff_cover/report_generator.py b/diff_cover/report_generator.py
@@ -11,14 +11,17 @@
 
 from diff_cover.snippets import Snippet
 from diff_cover.util import to_unix_path
+from diff_cover.violationsreporters.base import Violation
 
 
 class DiffViolations:
     """
     Class to capture violations generated by a particular diff
     """
 
-    def __init__(self, violations, measured_lines, diff_lines):
+    def __init__(
+        self, violations, measured_lines, diff_lines, treat_unmeasured_as_uncovered=False
+    ):
         self.lines = {violation.line for violation in violations}.intersection(
             diff_lines
         )
@@ -36,13 +39,28 @@ def __init__(self, violations, measured_lines, diff_lines):
         else:
             self.measured_lines = set(measured_lines).intersection(diff_lines)
 
+            # When enabled and coverage data exists for this file,
+            # treat diff lines absent from the coverage report as uncovered.
+            if treat_unmeasured_as_uncovered and self.measured_lines:
+                unmeasured_diff_lines = set(diff_lines) - set(measured_lines)
+                for line_num in unmeasured_diff_lines:
+                    self.measured_lines.add(line_num)
+                    self.lines.add(line_num)
+                    self.violations.add(Violation(line_num, None))
+
 
 class BaseReportGenerator(ABC):
     """
     Generate a diff coverage report.
     """
 
-    def __init__(self, violations_reporter, diff_reporter, total_percent_float=False):
+    def __init__(
+        self,
+        violations_reporter,
+        diff_reporter,
+        total_percent_float=False,
+        treat_unmeasured_as_uncovered=False,
+    ):
         """
         Configure the report generator to build a report
         from `violations_reporter` (of type BaseViolationReporter)
@@ -51,6 +69,7 @@ def __init__(self, violations_reporter, diff_reporter, total_percent_float=False
         self._violations = violations_reporter
         self._diff = diff_reporter
         self._total_percent_float = total_percent_float
+        self._treat_unmeasured_as_uncovered = treat_unmeasured_as_uncovered
         self._diff_violations_dict = None
 
         self._cache_violations = None
@@ -204,6 +223,7 @@ def _diff_violations(self):
                         violations.get(to_unix_path(src_path), []),
                         self._violations.measured_lines(src_path),
                         self._diff.lines_changed(src_path),
+                        treat_unmeasured_as_uncovered=self._treat_unmeasured_as_uncovered,
                     )
                     for src_path in src_paths_changed
                 }
@@ -213,6 +233,7 @@ def _diff_violations(self):
                         self._violations.violations(src_path),
                         self._violations.measured_lines(src_path),
                         self._diff.lines_changed(src_path),
+                        treat_unmeasured_as_uncovered=self._treat_unmeasured_as_uncovered,
                     )
                     for src_path in src_paths_changed
                 }
@@ -295,11 +316,13 @@ def __init__(
         diff_reporter,
         css_url=None,
         total_percent_float=False,
+        treat_unmeasured_as_uncovered=False,
     ):
         super().__init__(
             violations_reporter,
             diff_reporter,
             total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         self.css_url = css_url
 
@@ -438,11 +461,13 @@ def __init__(
         diff_reporter,
         show_uncovered=False,
         total_percent_float=False,
+        treat_unmeasured_as_uncovered=False,
     ):
         super().__init__(
             violations_reporter,
             diff_reporter,
             total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         self.include_snippets = show_uncovered
 
@@ -464,11 +489,13 @@ def __init__(
         diff_reporter,
         annotations_type,
         total_percent_float=False,
+        treat_unmeasured_as_uncovered=False,
     ):
         super().__init__(
             violations_reporter,
             diff_reporter,
             total_percent_float=total_percent_float,
+            treat_unmeasured_as_uncovered=treat_unmeasured_as_uncovered,
         )
         self.annotations_type = annotations_type
 
diff --git a/tests/test_diff_reporter.py b/tests/test_diff_reporter.py
@@ -466,6 +466,45 @@ def test_git_diff_error(
             diff.lines_changed("subdir/file1.py")
 
 
+def test_blank_added_lines_excluded(diff, git_diff):
+    """Blank/whitespace-only added lines should be excluded from lines_changed()."""
+    diff_str = dedent("""
+        diff --git a/file.py b/file.py
+        @@ -1,3 +1,6 @@
+         existing line
+        +
+        +def something():
+        +    print("hello")
+        +
+        +
+        """)
+
+    _set_git_diff_output(diff, git_diff, diff_str, "", "")
+
+    lines_changed = diff.lines_changed("file.py")
+    # Lines 2, 5, 6 are blank/whitespace-only, should be excluded
+    # Only lines 3 and 4 (non-blank added lines) should be included
+    assert lines_changed == [3, 4]
+
+
+def test_whitespace_only_added_lines_excluded(diff, git_diff):
+    """Added lines with only spaces/tabs should be excluded from lines_changed()."""
+    diff_str = dedent("""
+        diff --git a/file.py b/file.py
+        @@ -1,1 +1,4 @@
+         existing line
+        +    \t
+        +code_line
+        +
+        """)
+
+    _set_git_diff_output(diff, git_diff, diff_str, "", "")
+
+    lines_changed = diff.lines_changed("file.py")
+    # Only line 3 (code_line) should be included
+    assert lines_changed == [3]
+
+
 def test_plus_sign_in_hunk_bug(diff, git_diff):
     # This was a bug that caused a parse error
     diff_str = dedent("""
diff --git a/tests/test_report_generator.py b/tests/test_report_generator.py
@@ -613,6 +613,97 @@ def test_multiple_snippets(self):
         self.assert_report(expected)
 
 
+class TestTreatUnmeasuredAsUncovered(BaseReportGeneratorTest):
+    """Tests for the treat_unmeasured_as_uncovered flag."""
+
+    @pytest.fixture
+    def report(self, coverage, diff):
+        return SimpleReportGenerator(
+            coverage, diff, treat_unmeasured_as_uncovered=True
+        )
+
+    def test_unmeasured_diff_lines_become_violations(
+        self, diff, diff_lines_changed, coverage_violations, coverage_measured_lines
+    ):
+        """When flag is enabled, diff lines absent from measured_lines become violations."""
+        diff.src_paths_changed.return_value = ["file.py"]
+        # Diff has lines 1, 2, 3
+        diff_lines_changed.update({"file.py": [1, 2, 3]})
+        # Coverage only measures line 1 (with a hit)
+        coverage_measured_lines.update({"file.py": [1]})
+        coverage_violations.update({"file.py": []})
+
+        # Lines 2 and 3 are unmeasured, should become violations
+        assert self.report.total_num_lines() == 3
+        assert self.report.total_num_violations() == 2
+        assert sorted(self.report.violation_lines("file.py")) == [2, 3]
+
+    def test_empty_measured_lines_no_expansion(
+        self, diff, diff_lines_changed, coverage_violations, coverage_measured_lines
+    ):
+        """When measured_lines is empty (file not in coverage), no expansion happens."""
+        diff.src_paths_changed.return_value = ["file.py"]
+        diff_lines_changed.update({"file.py": [1, 2, 3]})
+        # Empty measured lines means file is not in coverage report
+        coverage_measured_lines.update({"file.py": []})
+        coverage_violations.update({"file.py": []})
+
+        # No measured lines means no expansion
+        assert self.report.total_num_lines() == 0
+        assert self.report.total_num_violations() == 0
+
+    def test_measured_lines_none_no_expansion(
+        self, diff, diff_lines_changed, coverage_violations, coverage_measured_lines
+    ):
+        """When measured_lines is None (quality reporters), all diff lines are measured."""
+        diff.src_paths_changed.return_value = ["file.py"]
+        diff_lines_changed.update({"file.py": [1, 2, 3]})
+        # None means all lines are measured (quality reporter convention)
+        coverage_measured_lines.update({"file.py": None})
+        coverage_violations.update({"file.py": []})
+
+        # All 3 lines measured, no violations
+        assert self.report.total_num_lines() == 3
+        assert self.report.total_num_violations() == 0
+
+    def test_existing_violations_plus_unmeasured(
+        self, diff, diff_lines_changed, coverage_violations, coverage_measured_lines
+    ):
+        """Existing violations are preserved alongside new unmeasured-line violations."""
+        diff.src_paths_changed.return_value = ["file.py"]
+        diff_lines_changed.update({"file.py": [1, 2, 3, 4]})
+        # Lines 1 and 2 are measured; line 2 is a violation
+        coverage_measured_lines.update({"file.py": [1, 2]})
+        coverage_violations.update({"file.py": [Violation(2, None)]})
+
+        # Line 2 is an existing violation, lines 3 and 4 are unmeasured -> violations
+        assert self.report.total_num_lines() == 4
+        assert self.report.total_num_violations() == 3
+        assert sorted(self.report.violation_lines("file.py")) == [2, 3, 4]
+
+
+class TestTreatUnmeasuredDisabled(BaseReportGeneratorTest):
+    """Tests to confirm default behavior (flag disabled) is preserved."""
+
+    @pytest.fixture
+    def report(self, coverage, diff):
+        return SimpleReportGenerator(coverage, diff)
+
+    def test_unmeasured_lines_not_flagged_by_default(
+        self, diff, diff_lines_changed, coverage_violations, coverage_measured_lines
+    ):
+        """With flag disabled, unmeasured diff lines are silently ignored."""
+        diff.src_paths_changed.return_value = ["file.py"]
+        diff_lines_changed.update({"file.py": [1, 2, 3]})
+        # Coverage only measures line 1
+        coverage_measured_lines.update({"file.py": [1]})
+        coverage_violations.update({"file.py": []})
+
+        # Only 1 measured line, no violations (lines 2,3 are ignored)
+        assert self.report.total_num_lines() == 1
+        assert self.report.total_num_violations() == 0
+
+
 class TestSimpleReportGeneratorWithBatchViolationReporter(BaseReportGeneratorTest):
 
     @pytest.fixture
