fuzzers->fuzz targets and finish affected_fuzz_targets module

1 files changed, 91 insertions, 9 deletions

diff --git a/infra/cifuzz/affected_fuzz_targets.py b/infra/cifuzz/affected_fuzz_targets.py
index ca81752b..b5f51ad6 100644
--- a/infra/cifuzz/affected_fuzz_targets.py
+++ b/infra/cifuzz/affected_fuzz_targets.py
@@ -11,7 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-"""Module for dealing with fuzzers affected by the change-under-test (CUT)."""
+"""Module for dealing with fuzz targets affected by the change-under-test
+(CUT)."""
+import logging
 import os
 import sys
 
@@ -21,11 +23,91 @@ sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 import utils
 
 
-def fix_git_repo_for_diff(repo_dir):
-  """Fixes git repos cloned by the "checkout" action so that diffing works on
-  them."""
-  command = [
-      'git', 'symbolic-ref', 'refs/remotes/origin/HEAD',
-      'refs/remotes/origin/master'
-  ]
-  return utils.execute(command, location=repo_dir)
+def remove_unaffected_fuzz_targets(project_name, out_dir, files_changed,
+                                   repo_path):
+  """Removes all non affected fuzz targets in the out directory.
+
+  Args:
+    project_name: The name of the relevant OSS-Fuzz project.
+    out_dir: The location of the fuzz target binaries.
+    files_changed: A list of files changed compared to HEAD.
+    repo_path: The location of the OSS-Fuzz repo in the docker image.
+
+  This function will not delete fuzz targets unless it knows that the fuzz
+  targets are unaffected. For example, this means that fuzz targets which don't
+  have coverage data on will not be deleted.
+  """
+  if not files_changed:
+    # Don't remove any fuzz targets if there is no difference from HEAD.
+    logging.info('No files changed.')
+    return
+
+  logging.info('Files changed in PR: %s', files_changed)
+
+  fuzz_target_paths = utils.get_fuzz_targets(out_dir)
+  if not fuzz_target_paths:
+    # Nothing to remove.
+    logging.error('No fuzz targets found in out dir.')
+    return
+
+  coverage_getter = coverage.OSSFuzzCoveragGetter(project_name,
+                                                  repo_path)
+  if coverage_getter.fuzzer_stats_url:
+    # Don't remove any fuzz targets unless we have data.
+    logging.error('Could not download latest coverage report.')
+    return
+
+  affected_fuzz_targets = get_affected_fuzz_targets(
+      coverage_getter, fuzz_target_paths, files_changed)
+
+  if not affected_fuzz_targets:
+    logging.info('No affected fuzz targets detected, keeping all as fallback.')
+    return
+
+  logging.info('Using affected fuzz targets: %s.', affected_fuzz_targets)
+  unaffected_fuzz_targets = set(fuzz_target_paths) - affected_fuzz_targets
+  logging.info('Removing unaffected fuzz targets: %s.', unaffected_fuzz_targets)
+
+  # Remove all the targets that are not affected.
+  for fuzz_target_path in unaffected_fuzz_targets:
+    try:
+      os.remove(fuzz_target_path)
+    except OSError as error:
+      logging.error('%s occurred while removing file %s',
+                    error, fuzz_target_path)
+
+
+def is_fuzz_target_affected(coverage_getter, fuzz_target_path, files_changed):
+  """Returns True if a fuzz target (|fuzz_target_path| is affected by
+  |files_changed|."""
+  fuzz_target = os.path.basename(fuzz_target_path)
+  covered_files = coverage_getter.get_files_covered_by_target(fuzz_target)
+  if not covered_files:
+    # Assume a fuzz target is affected if we can't get its coverage from
+    # OSS-Fuzz.
+    logging.info('Could not get coverage for %s. Treating as affected.',
+                 fuzz_target)
+    return True
+
+  logging.info('Fuzz target %s is affected by: %s',
+               fuzz_target, covered_files)
+  for filename in files_changed:
+    if filename in covered_files:
+      logging.info('Fuzz target %s is affected by changed file: %s',
+                   fuzz_target, filename)
+      return True
+
+  logging.info('Fuzz target %s is not affected.', fuzz_target)
+  return False
+
+
+def get_affected_fuzz_targets(
+    coverage_getter, fuzz_target_paths, files_changed):
+  """Returns a list of paths of affected targets."""
+  affected_fuzz_targets = set()
+  for fuzz_target_path in fuzz_target_paths:
+    if is_fuzz_target_affected(
+        coverage_getter, fuzz_target_path, files_changed):
+      affected_fuzz_targets.add(fuzz_target_path)
+
+  return affected_fuzz_targets