Enable deltas reporting on pushes (#64)

Previously, the action only allowed reporting of memory usage change when the workflow was triggered by a pull_request event. This meant the action could only be used to determine the impact of changes proposed via pull requests. This information can also be useful to have either when pushing commits to a feature branch in preparation for a pull request, or for development work flows where pull requests are not always used (as is very common for individual Arduino projects).

This will result in longer push triggered workflow run duration for people with the enable-size-deltas input set to true, but no other impact. If the previous behavior of only reporting deltas for workflows triggered by a pull_request event is desired, this can be achieved using GitHub Actions expression syntax , by changing the enable-size-deltas input's value from true to ${{ github.event_name == 'pull_request' }}.

Author: per1234

README.md

@@ -119,7 +119,7 @@ GitHub access token used to get information from the GitHub API. Only needed if
 
 ### `enable-size-deltas-report`
 
-Set to `true` to cause the action to determine the change in memory usage of the compiled sketches between the pull request branch and the tip of the pull request's base branch. This may be used with the [`arduino/actions/libraries/report-size-deltas` action](https://github.com/arduino/actions/tree/master/libraries/report-size-deltas). Default `false`.
+Set to `true` to cause the action to determine the change in memory usage of the compiled sketches. If the workflow is triggered by a `pull_request` event, the comparison is between the pull request branch and the tip of the pull request's base branch. If the workflow is triggered by a `push` event, the comparison is between the pushed commit and its immediate parent. This may be used with the [`arduino/actions/libraries/report-size-deltas` action](https://github.com/arduino/actions/tree/master/libraries/report-size-deltas). Default `false`.
 
 ## Example usage
 

action.yml

@@ -26,7 +26,7 @@ inputs:
     description: 'GitHub access token used to get information from the GitHub API. Only needed if you are using the size deltas report feature with a private repository.'
     default: ''
   enable-size-deltas-report:
-    description: 'Set to true to cause the action to determine the change in memory usage of the compiled sketches between the head and base refs of a PR'
+    description: 'Set to true to cause the action to determine the change in memory usage of the compiled sketches between the head and base refs of a PR and the immediate parent commit of a push'
     default: false
 runs:
   using: 'docker'

compilesketches/compilesketches.py

@@ -126,6 +126,8 @@ def __init__(self, cli_version, fqbn_arg, platforms, libraries, sketch_paths, ve
         else:
             self.github_api = github.Github(login_or_token=github_token)
 
+        self.deltas_base_ref = self.get_deltas_base_ref()
+
         self.enable_size_deltas_report = parse_boolean_input(boolean_input=enable_size_deltas_report)
         # The enable-size-deltas-report input has a default value so it should always be either True or False
         if self.enable_size_deltas_report is None:
@@ -134,6 +136,31 @@ def __init__(self, cli_version, fqbn_arg, platforms, libraries, sketch_paths, ve
 
         self.sketches_report_path = pathlib.PurePath(sketches_report_path)
 
+    def get_deltas_base_ref(self):
+        """Return the Git ref to make deltas comparisons against."""
+        if os.environ["GITHUB_EVENT_NAME"] == "pull_request":
+            # For pull requests, the comparison is done against the PR's base branch
+            return self.get_pull_request_base_ref()
+        else:
+            # For pushes, the base ref is the immediate parent
+            return get_parent_commit_ref()
+
+    def get_pull_request_base_ref(self):
+        """Return the name of the pull request's base branch."""
+        # Determine the pull request number, to use for the GitHub API request
+        with open(file=os.environ["GITHUB_EVENT_PATH"]) as github_event_file:
+            pull_request_number = json.load(github_event_file)["pull_request"]["number"]
+
+        # Get the PR's base ref from the GitHub API
+        try:
+            repository_api = self.github_api.get_repo(full_name_or_id=os.environ["GITHUB_REPOSITORY"])
+        except github.UnknownObjectException:
+            print("::error::Unable to access repository data. Please specify the github-token input in your "
+                  "workflow configuration.")
+            sys.exit(1)
+
+        return repository_api.get_pull(number=pull_request_number).base.ref
+
     def compile_sketches(self):
         """Do compilation tests and record data."""
         self.install_arduino_cli()
@@ -768,19 +795,19 @@ def get_sketch_report(self, compilation_result):
         current_sizes = self.get_sizes_from_output(compilation_result=compilation_result)
         previous_sizes = None
         if self.do_size_deltas_report(compilation_result=compilation_result, current_sizes=current_sizes):
-            # Get data for the sketch at the tip of the target repository's default branch
-            # Get the pull request's head ref
+            # Get data for the sketch at the base ref
+            # Get the head ref
             repository = git.Repo(path=os.environ["GITHUB_WORKSPACE"])
             original_git_ref = repository.head.object.hexsha
 
-            # git checkout the PR's base ref
-            self.checkout_pull_request_base_ref()
+            # git checkout the base ref
+            self.checkout_deltas_base_ref()
 
             # Compile the sketch again
             print("Compiling previous version of sketch to determine memory usage change")
             previous_compilation_result = self.compile_sketch(sketch_path=compilation_result.sketch)
 
-            # git checkout the PR's head ref to return the repository to its previous state
+            # git checkout the head ref to return the repository to its previous state
             repository.git.checkout(original_git_ref)
 
             previous_sizes = self.get_sizes_from_output(compilation_result=previous_compilation_result)
@@ -855,37 +882,22 @@ def do_size_deltas_report(self, compilation_result, current_sizes):
         """
         return (
             self.enable_size_deltas_report
-            and os.environ["GITHUB_EVENT_NAME"] == "pull_request"
             and compilation_result.success
             and any(size.get(self.ReportKeys.absolute) != self.not_applicable_indicator for
                     size in current_sizes)
         )
 
-    def checkout_pull_request_base_ref(self):
-        """git checkout the base ref of the pull request"""
+    def checkout_deltas_base_ref(self):
+        """git checkout the base ref of the deltas comparison"""
         repository = git.Repo(path=os.environ["GITHUB_WORKSPACE"])
 
-        # Determine the pull request number, to use for the GitHub API request
-        with open(file=os.environ["GITHUB_EVENT_PATH"]) as github_event_file:
-            pull_request_number = json.load(github_event_file)["pull_request"]["number"]
-
-        # Get the PR's base ref from the GitHub API
-        try:
-            repository_api = self.github_api.get_repo(full_name_or_id=os.environ["GITHUB_REPOSITORY"])
-        except github.UnknownObjectException:
-            print("::error::Unable to access repository data. Please specify the github-token input in your workflow"
-                  " configuration.")
-            sys.exit(1)
-
-        pull_request_base_ref = repository_api.get_pull(number=pull_request_number).base.ref
-
-        # git fetch the PR's base ref
+        # git fetch the deltas base ref
         origin_remote = repository.remotes["origin"]
-        origin_remote.fetch(refspec=pull_request_base_ref, verbose=self.verbose, no_tags=True, prune=True,
+        origin_remote.fetch(refspec=self.deltas_base_ref, verbose=self.verbose, no_tags=True, prune=True,
                             depth=1)
 
-        # git checkout the PR base ref
-        repository.git.checkout(pull_request_base_ref)
+        # git checkout the deltas base ref
+        repository.git.checkout(self.deltas_base_ref)
 
     def get_sizes_report(self, current_sizes, previous_sizes):
         """Return a list containing all memory usage data assembled.
@@ -1101,6 +1113,12 @@ def parse_boolean_input(boolean_input):
     return parsed_boolean_input
 
 
+def get_parent_commit_ref():
+    """Return the Git ref of the immediate parent commit."""
+    repository_object = git.Repo(path=os.environ["GITHUB_WORKSPACE"])
+    return repository_object.head.object.parents[0].hexsha
+
+
 def path_relative_to_workspace(path):
     """Returns the path relative to the workspace of the action's Docker container. This is the path used in all
     human-targeted output.