Add expand_coverage_report option to for #270 (#416)

* Add expand_coverage_report option to  add missing lines in a coverage report based on the previous line hit score

* run black

* adds .venv to .gitignore

* changes expand-coverage-report argument to use - instead of _

* Revert "changes expand-coverage-report argument to use - instead of _"

This reverts commit 381d2b4.

* changes expand-coverage-report argument to use - instead of _

* documents --expand-coverage-report in README.rst

* adds tests to expand-coverage-report

* fix readme styling issues

* Fix trailing white space on readme 287

Author: MathieuLamiot

.gitignore

@@ -4,6 +4,7 @@
 .idea
 venv
 27venv
+.venv
 
 # C extensions
 *.so

README.rst

@@ -274,6 +274,18 @@ It can be enabled by using the ``-q``/``--quiet`` flag:
 
 If enabled, the tool will only print errors and failures but no information or warning messages.
 
+Compatibility with multi-line statements
+----------------------------------------
+``diff-cover`` relies on the comparison of diff reports and coverage reports, and does not report
+lines that appear in one and not in the other. While diff reports list all lines that changed,
+coverage reports usually list code statements. As a result, a change in a multi-line statement may not be analyzed by ``diff-cover``.
+
+As a workaround, you can use the argument ``--expand-coverage-report``: lines not appearing in the coverage reports will be added to them with the same number of hits as the previously reported line. ``diff-cover`` will then perform diff coverage analysis on all changed lines.
+
+Notes:
+- This argument is only available for XML coverage reports.
+- This workaround is designed under the assumption that the coverage tool reports untested statements with hits set to 0, and it reports statements based on the opening line.
+
 Configuration files
 -------------------
 Both tools allow users to specify the options in a configuration file with `--config-file`/`-c`:

diff_cover/diff_cover_tool.py

@@ -41,6 +41,9 @@
 )
 QUIET_HELP = "Only print errors and failures"
 SHOW_UNCOVERED = "Show uncovered lines on the console"
+EXPAND_COVERAGE_REPORT = (
+    "Append missing lines in coverage reports based on the hits of the previous line."
+)
 INCLUDE_UNTRACKED_HELP = "Include untracked files"
 CONFIG_FILE_HELP = "The configuration file to use"
 DIFF_FILE_HELP = "The diff file to use"
@@ -93,6 +96,13 @@ def parse_coverage_args(argv):
         "--show-uncovered", action="store_true", default=None, help=SHOW_UNCOVERED
     )
 
+    parser.add_argument(
+        "--expand-coverage-report",
+        action="store_true",
+        default=None,
+        help=EXPAND_COVERAGE_REPORT,
+    )
+
     parser.add_argument(
         "--external-css-file",
         metavar="FILENAME",
@@ -183,6 +193,7 @@ def parse_coverage_args(argv):
         "ignore_whitespace": False,
         "diff_range_notation": "...",
         "quiet": False,
+        "expand_coverage_report": False,
     }
 
     return get_config(parser=parser, argv=argv, defaults=defaults, tool=Tool.DIFF_COVER)
@@ -204,6 +215,7 @@ def generate_coverage_report(
     src_roots=None,
     quiet=False,
     show_uncovered=False,
+    expand_coverage_report=False,
 ):
     """
     Generate the diff coverage report, using kwargs from `parse_args()`.
@@ -231,7 +243,7 @@ def generate_coverage_report(
     if len(xml_roots) > 0 and len(lcov_roots) > 0:
         raise ValueError(f"Mixing LCov and XML reports is not supported yet")
     elif len(xml_roots) > 0:
-        coverage = XmlCoverageReporter(xml_roots, src_roots)
+        coverage = XmlCoverageReporter(xml_roots, src_roots, expand_coverage_report)
     else:
         coverage = LcovCoverageReporter(lcov_roots, src_roots)
 
@@ -308,6 +320,7 @@ def main(argv=None, directory=None):
         src_roots=arg_dict["src_roots"],
         quiet=quiet,
         show_uncovered=arg_dict["show_uncovered"],
+        expand_coverage_report=arg_dict["expand_coverage_report"],
     )
 
     if percent_covered >= fail_under:

diff_cover/violationsreporters/violations_reporter.py

@@ -24,7 +24,7 @@ class XmlCoverageReporter(BaseViolationReporter):
     Query information from a Cobertura|Clover|JaCoCo XML coverage report.
     """
 
-    def __init__(self, xml_roots, src_roots=None):
+    def __init__(self, xml_roots, src_roots=None, expand_coverage_report=False):
         """
         Load the XML coverage report represented
         by the cElementTree with root element `xml_root`.
@@ -41,6 +41,7 @@ def __init__(self, xml_roots, src_roots=None):
         self._xml_cache = [{} for i in range(len(xml_roots))]
 
         self._src_roots = src_roots or [""]
+        self._expand_coverage_report = expand_coverage_report
 
     def _get_xml_classes(self, xml_document):
         """
@@ -216,6 +217,28 @@ def _cache_file(self, src_path):
                 if line_nodes is None:
                     continue
 
+                # Expand coverage report with not reported lines
+                if self._expand_coverage_report:
+                    reported_line_hits = {}
+                    for line in line_nodes:
+                        reported_line_hits[int(line.get(_number))] = int(
+                            line.get(_hits, 0)
+                        )
+                    if reported_line_hits:
+                        last_hit_number = 0
+                        for line_number in range(
+                            min(reported_line_hits.keys()),
+                            max(reported_line_hits.keys()),
+                        ):
+                            if line_number in reported_line_hits:
+                                last_hit_number = reported_line_hits[line_number]
+                            else:
+                                # This is an unreported line.
+                                # We add it with the previous line hit score
+                                line_nodes.append(
+                                    {_hits: last_hit_number, _number: line_number}
+                                )
+
                 # First case, need to define violations initially
                 if violations is None:
                     violations = {

tests/fixtures/coverage_missing_lines.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" ?>
+<!DOCTYPE coverage
+  SYSTEM 'http://cobertura.sourceforge.net/xml/coverage-03.dtd'>
+<coverage branch-rate="0" line-rate="0.8792" timestamp="1371471706873" version="3.6">
+	<packages>
+		<package branch-rate="0" complexity="0" line-rate="0.9915" name="">
+			<classes>
+                <class branch-rate="0" complexity="0" filename="test_src.txt" line-rate="0.9643" name="test_src.txt">
+					<methods/>
+					<lines>
+						<line hits="1" number="1"/>
+						<line hits="0" number="2"/>
+						<line hits="0" number="4"/>
+						<line hits="1" number="5"/>
+						<line hits="1" number="7"/>
+						<line hits="0" number="8"/>
+						<line hits="1" number="9"/>
+						<line hits="0" number="10"/>
+					</lines>
+				</class>
+			</classes>
+		</package>
+	</packages>
+</coverage>

tests/fixtures/expand_console_report.txt

@@ -0,0 +1,10 @@
+-------------
+Diff Coverage
+Diff: origin/main...HEAD, staged and unstaged changes
+-------------
+test_src.txt (50.0%): Missing lines 2-4,8,10
+-------------
+Total:   10 lines
+Missing: 5 lines
+Coverage: 50%
+-------------

tests/test_integration.py

@@ -412,6 +412,20 @@ def test_show_uncovered_lines_console(self):
             ["diff-cover", "--show-uncovered", "coverage.xml"],
         )
 
+    def test_expand_coverage_report_complete_report(self):
+        self._check_console_report(
+            "git_diff_add.txt",
+            "add_console_report.txt",
+            ["diff-cover", "coverage.xml", "--expand-coverage-report"],
+        )
+
+    def test_expand_coverage_report_uncomplete_report(self):
+        self._check_console_report(
+            "git_diff_add.txt",
+            "expand_console_report.txt",
+            ["diff-cover", "coverage_missing_lines.xml", "--expand-coverage-report"],
+        )
+
 
 class TestDiffQualityIntegration(ToolsIntegrationBase):
     """

tests/test_violations_reporter.py

@@ -66,6 +66,21 @@ class TestXmlCoverageReporterTest:
     ONE_VIOLATION = {Violation(11, None)}
     VERY_MANY_MEASURED = {2, 3, 5, 7, 11, 13, 17, 23, 24, 25, 26, 26, 27}
 
+    MANY_VIOLATIONS_EXPANDED_MANY_MEASURED = {
+        Violation(3, None),
+        Violation(4, None),
+        Violation(7, None),
+        Violation(8, None),
+        Violation(9, None),
+        Violation(10, None),
+        Violation(11, None),
+        Violation(12, None),
+        Violation(13, None),
+        Violation(14, None),
+        Violation(15, None),
+        Violation(16, None),
+    }
+
     @pytest.fixture(autouse=True)
     def patch_git_patch(self, mocker):
         # Paths generated by git_path are always the given argument
@@ -266,6 +281,52 @@ def test_no_such_file(self):
         result = coverage.violations("file.py")
         assert result == set()
 
+    def test_expand_unreported_lines_when_configured(self):
+        # Construct the XML report
+        file_paths = ["file1.java"]
+        # fixture
+        violations = self.MANY_VIOLATIONS
+        measured = self.MANY_MEASURED
+        xml = self._coverage_xml(file_paths, violations, measured)
+
+        # Parse the reports
+        coverage = XmlCoverageReporter([xml], expand_coverage_report=True)
+
+        # Expect that the name is set
+        assert coverage.name() == "XML"
+
+        # By construction, each file has the same set
+        # of covered/uncovered lines
+        assert self.MANY_VIOLATIONS_EXPANDED_MANY_MEASURED == coverage.violations(
+            "file1.java"
+        )
+
+    def test_expand_unreported_lines_without_violations(self):
+        # Construct the XML report
+        file_paths = ["file1.java"]
+        # fixture
+        violations = {}
+        measured = self.MANY_MEASURED
+        xml = self._coverage_xml(file_paths, violations, measured)
+
+        # Parse the reports
+        coverage = XmlCoverageReporter([xml], expand_coverage_report=True)
+
+        assert set() == coverage.violations("file1.java")
+
+    def test_expand_unreported_lines_without_measured(self):
+        # Construct the XML report
+        file_paths = ["file1.java"]
+        # fixture
+        violations = {}
+        measured = {}
+        xml = self._coverage_xml(file_paths, violations, measured)
+
+        # Parse the reports
+        coverage = XmlCoverageReporter([xml], expand_coverage_report=True)
+
+        assert set() == coverage.violations("file1.java")
+
     def _coverage_xml(self, file_paths, violations, measured, source_paths=None):
         """
         Build an XML tree with source files specified by `file_paths`.