fix: Warn users when GitHub Actions is making a merge commit

Makefile

@@ -22,7 +22,7 @@ test:
 test_setup:
 	mkdir -p ${CODE_PATH}
 	cd ${CODE_PATH} && ls -A1 | xargs rm -rf
-	git clone https://github.com/DeepSourceCorp/cli ${CODE_PATH}
+	git clone https://github.com/DeepSourceCorp/july ${CODE_PATH}
 	chmod +x /tmp/deepsource
 	cp ./command/report/tests/golden_files/python_coverage.xml /tmp
 

command/report/git.go

@@ -11,29 +11,31 @@ import (
 )
 
 // gitGetHead accepts a git directory and returns head commit OID / error
-func gitGetHead(workspaceDir string) (string, error) {
+func gitGetHead(workspaceDir string) (headOID string, warning string, err error) {
+	// Check if DeepSource's Test coverage action triggered this first before executing any git commands.
+	headOID, err = getTestCoverageActionCommit()
+	if headOID != "" {
+		return
+	}
+
+	// get the top commit manually, using git command
+	headOID, err = fetchHeadManually(workspaceDir)
+	if err != nil {
+		fmt.Println(err)
+		sentry.CaptureException(err)
+		return
+	}
+
 	// TRAVIS CI
-	// Get USER env variable.
 	if envUser := os.Getenv("USER"); envUser == "travis" {
-		// Travis creates a merge commit for pull requests on forks.
-		// The head of commit is this merge commit, which does not match the commit of deepsource check.
-		// Fetch value of pull request SHA. If this is a PR, it will return SHA of HEAD commit of the PR, else "".
-		// If prSHA is not empty, that means we got an SHA, which is HEAD. Return this.
-		if prSHA := os.Getenv("TRAVIS_PULL_REQUEST_SHA"); len(prSHA) > 0 {
-			return prSHA, nil
-		}
+		headOID, warning, err = getTravisCommit(headOID)
+		return
 	}
 
 	// GITHUB ACTIONS
-	// Check if it is a GitHub Action Environment
-	// If it is: then get the HEAD from `GITHUB_SHA` environment
 	if _, isGitHubEnv := os.LookupEnv("GITHUB_ACTIONS"); isGitHubEnv {
-		// When GITHUB_REF is not set, GITHUB_SHA points to original commit.
-		// When set, it points to the "latest *merge* commit in the branch".
-		// Ref: https://help.github.com/en/actions/reference/events-that-trigger-workflows#pull-request-event-pull_request
-		if _, isBranchCommit := os.LookupEnv("GITHUB_REF"); !isBranchCommit {
-			return os.Getenv("GITHUB_SHA"), nil
-		}
+		headOID, warning, err = getGitHubActionsCommit(headOID)
+		return
 	}
 
 	// Check if the `GIT_COMMIT_SHA` environment variable exists. If yes, return this as
@@ -47,18 +49,11 @@ func gitGetHead(workspaceDir string) (string, error) {
 	// GIT_COMMIT_SHA=$(git --no-pager rev-parse HEAD | tr -d '\n')
 	// docker run -e DEEPSOURCE_DSN -e GIT_COMMIT_SHA ...
 	if _, isManuallyInjectedSHA := os.LookupEnv("GIT_COMMIT_SHA"); isManuallyInjectedSHA {
-		return os.Getenv("GIT_COMMIT_SHA"), nil
+		return os.Getenv("GIT_COMMIT_SHA"), "", nil
 	}
 
-	// If we are here, it means this is neither GitHub Action on default branch,
-	// nor a travis env with PR. Continue to fetch the headOID via the git command.
-	headOID, err := fetchHeadManually(workspaceDir)
-	if err != nil {
-		fmt.Println(err)
-		sentry.CaptureException(err)
-		return "", err
-	}
-	return headOID, nil
+	// If we are here, it means there weren't any special cases. Return the manually found headOID.
+	return
 }
 
 // Fetches the latest commit hash using the command `git rev-parse HEAD`
@@ -80,3 +75,60 @@ func fetchHeadManually(directoryPath string) (string, error) {
 	// Trim newline suffix from Commit OID
 	return strings.TrimSuffix(outStr, "\n"), nil
 }
+
+// Handle special cases for GitHub Actions.
+func getGitHubActionsCommit(topCommit string) (headOID string, warning string, err error) {
+	// When GITHUB_REF is not set, GITHUB_SHA points to original commit.
+	// When set, it points to the "latest *merge* commit in the branch".
+	// Early exit when GITHUB_SHA points to the original commit.
+	// Ref: https://help.github.com/en/actions/reference/events-that-trigger-workflows#pull-request-event-pull_request
+	if _, isRefPresent := os.LookupEnv("GITHUB_REF"); !isRefPresent {
+		headOID = os.Getenv("GITHUB_SHA")
+		return
+	}
+
+	// Case: Detect Merge commit made by GitHub Actions, which pull_request events are nutorious to make.
+	// We are anyways going to return `headOID` fetched manually, but want to warn users about the merge commit.
+
+	// When ref is not provided during the checkout step, headOID would be the same as GITHUB_SHA
+	// This confirms the merge commit.
+	// event names where GITHUB_SHA would be of a merge commit:
+	//    "pull_request",
+	// 	  "pull_request_review",
+	// 	  "pull_request_review",
+	// 	  "pull_request_review_comment",
+	eventName := os.Getenv("GITHUB_EVENT_NAME")
+	eventCommitSha := os.Getenv("GITHUB_SHA")
+	if strings.HasPrefix(eventName, "pull_request") && topCommit == eventCommitSha {
+		warning = "Warning: Looks like the checkout step is making a merge commit. " +
+			"Test coverage Analyzer would not run for the reported artifact because the merge commit doesn't exist upstream.\n" +
+			"Please refer to the docs for required changes. Ref: https://docs.deepsource.com/docs/analyzers-test-coverage#with-github-actions"
+	}
+	headOID = topCommit
+	return
+}
+
+// Return PR's HEAD ref set as env variable manually by DeepSource's Test coverage action.
+func getTestCoverageActionCommit() (headOID string, err error) {
+	// This is kept separate from `getGitHubActionsCommit` because we don't want to run any git command manually
+	// before this is checked. Since this is guaranteed to be set if artifact is sent using our GitHub action,
+	// we can reliably send the commit SHA, and no git commands are executed, making the actions work all the time. \o/
+
+	// We are setting PR's head commit as default using github context as env variable: "GHA_HEAD_COMMIT_SHA"
+	headOID = os.Getenv("GHA_HEAD_COMMIT_SHA")
+
+	return
+}
+
+// Handle special case for TravisCI
+func getTravisCommit(topCommit string) (string, string, error) {
+	// Travis creates a merge commit for pull requests on forks.
+	// The head of commit is this merge commit, which does not match the commit of deepsource check.
+	// Fetch value of pull request SHA. If this is a PR, it will return SHA of HEAD commit of the PR, else "".
+	// If prSHA is not empty, that means we got an SHA, which is HEAD. Return this.
+	if prSHA := os.Getenv("TRAVIS_PULL_REQUEST_SHA"); len(prSHA) > 0 {
+		return prSHA, "", nil
+	}
+
+	return topCommit, "", nil
+}

command/report/report.go

@@ -179,7 +179,7 @@ func (opts *ReportOptions) Run() int {
 	dsnAccessToken := dsnSplitTokenHost[0]
 
 	// Head Commit OID
-	headCommitOID, err := gitGetHead(currentDir)
+	headCommitOID, warning, err := gitGetHead(currentDir)
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "DeepSource | Error | Unable to get commit OID HEAD. Make sure you are running the CLI from a git repository")
 		sentry.CaptureException(err)
@@ -375,5 +375,8 @@ func (opts *ReportOptions) Run() int {
 	if queryResponse.Data.CreateArtifact.Message != "" {
 		fmt.Printf("Message   %s\n", queryResponse.Data.CreateArtifact.Message)
 	}
+	if warning != "" {
+		fmt.Print(warning)
+	}
 	return 0
 }