py-cov-action · ewjoachim · Jul 13, 2025 · Apr 21, 2025 · May 26, 2025 · May 26, 2025
diff --git a/coverage_comment/coverage.py b/coverage_comment/coverage.py
@@ -286,18 +286,7 @@ def get_diff_coverage_info(
     )
 
 
-def get_added_lines(
-    git: subprocess.Git, base_ref: str
-) -> dict[pathlib.Path, list[int]]:
-    # --unified=0 means we don't get any context lines for chunk, and we
-    # don't merge chunks. This means the headers that describe line number
-    # are always enough to derive what line numbers were added.
-    git.fetch("origin", base_ref, "--depth=1000")
-    diff = git.diff("--unified=0", "FETCH_HEAD", "--", ".")
-    return parse_diff_output(diff)
-
-
-def parse_diff_output(diff: str) -> dict[pathlib.Path, list[int]]:
+def get_added_lines(diff: str) -> dict[pathlib.Path, list[int]]:
     current_file: pathlib.Path | None = None
     added_filename_prefix = "+++ b/"
     result: dict[pathlib.Path, list[int]] = {}

diff --git a/coverage_comment/github.py b/coverage_comment/github.py
@@ -254,3 +254,27 @@ def append_to_file(content: str, filepath: pathlib.Path):
 
 def add_job_summary(content: str, github_step_summary: pathlib.Path):
     append_to_file(content=content, filepath=github_step_summary)
+
+
+def get_pr_diff(github: github_client.GitHub, repository: str, pr_number: int) -> str:
+    """
+    Get the diff of a pull request.
+    """
+    return (
+        github.repos(repository)
+        .pulls(pr_number)
+        .get(headers={"Accept": "application/vnd.github.v3.diff"})
+    )
+
+
+def get_branch_diff(
+    github: github_client.GitHub, repository: str, base_branch: str, head_branch: str
+) -> str:
+    """
+    Get the diff of branch.
+    """
+    return (
+        github.repos(repository)
+        .compare(f"{base_branch}...{head_branch}")
+        .get(headers={"Accept": "application/vnd.github.v3.diff"})
+    )
diff --git a/coverage_comment/github_client.py b/coverage_comment/github_client.py
@@ -83,10 +83,7 @@ def _http(
             **header_kwargs,
             **requests_kwargs,
         )
-        if bytes:
-            contents = response.content
-        else:
-            contents = response_contents(response)
+        contents = response_contents(response=response, bytes=bytes)
 
         try:
             response.raise_for_status()
@@ -103,14 +100,15 @@ def _http(
 
 def response_contents(
     response: httpx.Response,
+    bytes: bool,
 ) -> JsonObject | str | bytes:
+    if bytes:
+        return response.content
+
     if response.headers.get("content-type", "").startswith("application/json"):
         return response.json(object_hook=JsonObject)
-    if response.headers.get("content-type", "").startswith(
-        "application/vnd.github.raw+json"
-    ):
-        return response.text
-    return response.content
+
+    return response.text
 
 
 class JsonObject(dict):

diff --git a/coverage_comment/main.py b/coverage_comment/main.py
@@ -132,7 +132,20 @@ def process_pr(
     )
     base_ref = config.GITHUB_BASE_REF or repo_info.default_branch
 
-    added_lines = coverage_module.get_added_lines(git=git, base_ref=base_ref)
+    if config.GITHUB_BRANCH_NAME:
+        diff = github.get_branch_diff(
+            github=gh,
+            repository=config.GITHUB_REPOSITORY,
+            base_branch=base_ref,
+            head_branch=config.GITHUB_BRANCH_NAME,
+        )
+    elif config.GITHUB_PR_NUMBER:
+        diff = github.get_pr_diff(
+            github=gh,
+            repository=config.GITHUB_REPOSITORY,
+            pr_number=config.GITHUB_PR_NUMBER,
+        )
+    added_lines = coverage_module.get_added_lines(diff=diff)
     diff_coverage = coverage_module.get_diff_coverage_info(
         coverage=coverage, added_lines=added_lines
     )

diff --git a/tests/integration/conftest.py b/tests/integration/conftest.py
@@ -0,0 +1,101 @@
+from __future__ import annotations
+
+import os
+import pathlib
+import subprocess
+import uuid
+
+import pytest
+
+
+@pytest.fixture
+def in_integration_env(integration_env, integration_dir):
+    curdir = os.getcwd()
+    os.chdir(integration_dir)
+    yield integration_dir
+    os.chdir(curdir)
+
+
+@pytest.fixture
+def integration_dir(tmp_path: pathlib.Path):
+    test_dir = tmp_path / "integration_test"
+    test_dir.mkdir()
+    return test_dir
+
+
+@pytest.fixture
+def file_path(integration_dir):
+    return integration_dir / "foo.py"
+
+
+@pytest.fixture
+def write_file(file_path):
+    def _(*variables):
+        content = "import os"
+        for i, var in enumerate(variables):
+            content += f"""\nif os.environ.get("{var}"):\n    {i}\n"""
+        file_path.write_text(content, encoding="utf8")
+
+    return _
+
+
+@pytest.fixture
+def run_coverage(file_path, integration_dir):
+    def _(*variables):
+        subprocess.check_call(
+            ["coverage", "run", "--parallel", file_path.name],
+            cwd=integration_dir,
+            env=os.environ | dict.fromkeys(variables, "1"),
+        )
+
+    return _
+
+
+@pytest.fixture
+def commit(integration_dir):
+    def _():
+        subprocess.check_call(
+            ["git", "add", "."],
+            cwd=integration_dir,
+        )
+        subprocess.check_call(
+            ["git", "commit", "-m", str(uuid.uuid4())],
+            cwd=integration_dir,
+            env={
+                "GIT_AUTHOR_NAME": "foo",
+                "GIT_AUTHOR_EMAIL": "foo",
+                "GIT_COMMITTER_NAME": "foo",
+                "GIT_COMMITTER_EMAIL": "foo",
+                "GIT_CONFIG_GLOBAL": "/dev/null",
+                "GIT_CONFIG_SYSTEM": "/dev/null",
+            },
+        )
+
+    return _
+
+
+@pytest.fixture
+def integration_env(integration_dir, write_file, run_coverage, commit, request):
+    subprocess.check_call(["git", "init", "-b", "main"], cwd=integration_dir)
+    # diff coverage reads the "origin/{...}" branch so we simulate an origin remote
+    subprocess.check_call(["git", "remote", "add", "origin", "."], cwd=integration_dir)
+    write_file("A", "B")
+    commit()
+
+    add_branch_mark = request.node.get_closest_marker("add_branches")
+    for additional_branch in add_branch_mark.args if add_branch_mark else []:
+        subprocess.check_call(
+            ["git", "switch", "-c", additional_branch],
+            cwd=integration_dir,
+        )
+
+    subprocess.check_call(
+        ["git", "switch", "-c", "branch"],
+        cwd=integration_dir,
+    )
+
+    write_file("A", "B", "C", "D")
+    commit()
+
+    run_coverage("A", "C")
+    subprocess.check_call(["git", "fetch", "origin"], cwd=integration_dir)
diff --git a/tests/integration/test_github.py b/tests/integration/test_github.py
@@ -444,3 +444,29 @@ def test_annotations(capsys):
 ::endgroup::"""
     output = capsys.readouterr()
     assert output.err.strip() == expected
+
+
+def test_get_pr_diff(gh, session):
+    session.register(
+        "GET",
+        "/repos/foo/bar/pulls/123",
+        headers={"Accept": "application/vnd.github.v3.diff"},
+    )(text="diff --git a/foo.py b/foo.py...")
+
+    result = github.get_pr_diff(github=gh, repository="foo/bar", pr_number=123)
+
+    assert result == "diff --git a/foo.py b/foo.py..."
+
+
+def test_get_branch_diff(gh, session):
+    session.register(
+        "GET",
+        "/repos/foo/bar/compare/main...feature",
+        headers={"Accept": "application/vnd.github.v3.diff"},
+    )(text="diff --git a/foo.py b/foo.py...")
+
+    result = github.get_branch_diff(
+        github=gh, repository="foo/bar", base_branch="main", head_branch="feature"
+    )
+
+    assert result == "diff --git a/foo.py b/foo.py..."