Support array expressions in runs-on (#2088)

* Support array expressions in runs-on

* Simplify appproach to use EvaluateYamlNode, fix case-sensitivity bug

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

cmd/platforms.go

@@ -15,7 +15,7 @@ func (i *Input) newPlatforms() map[string]string {
 	for _, p := range i.platforms {
 		pParts := strings.Split(p, "=")
 		if len(pParts) == 2 {
-			platforms[pParts[0]] = pParts[1]
+			platforms[strings.ToLower(pParts[0])] = pParts[1]
 		}
 	}
 	return platforms

pkg/runner/run_context.go

@@ -626,14 +626,7 @@ func (rc *RunContext) containerImage(ctx context.Context) string {
 }
 
 func (rc *RunContext) runsOnImage(ctx context.Context) string {
-	job := rc.Run.Job()
+	for _, platformName := range rc.runsOnPlatformNames(ctx) {
-
-	if job.RunsOn() == nil {
-		common.Logger(ctx).Errorf("'runs-on' key not defined in %s", rc.String())
-	}
-
-	for _, runnerLabel := range job.RunsOn() {
-		platformName := rc.ExprEval.Interpolate(ctx, runnerLabel)
 		image := rc.Config.Platforms[strings.ToLower(platformName)]
 		if image != "" {
 			return image
@@ -643,6 +636,22 @@ func (rc *RunContext) runsOnImage(ctx context.Context) string {
 	return ""
 }
 
+func (rc *RunContext) runsOnPlatformNames(ctx context.Context) []string {
+	job := rc.Run.Job()
+
+	if job.RunsOn() == nil {
+		common.Logger(ctx).Errorf("'runs-on' key not defined in %s", rc.String())
+		return []string{}
+	}
+
+	if err := rc.ExprEval.EvaluateYamlNode(ctx, &job.RawRunsOn); err != nil {
+		common.Logger(ctx).Errorf("Error while evaluating runs-on: %v", err)
+		return []string{}
+	}
+
+	return job.RunsOn()
+}
+
 func (rc *RunContext) platformImage(ctx context.Context) string {
 	if containerImage := rc.containerImage(ctx); containerImage != "" {
 		return containerImage
@@ -684,12 +693,7 @@ func (rc *RunContext) isEnabled(ctx context.Context) (bool, error) {
 
 	img := rc.platformImage(ctx)
 	if img == "" {
-		if job.RunsOn() == nil {
+		for _, platformName := range rc.runsOnPlatformNames(ctx) {
-			l.Errorf("'runs-on' key not defined in %s", rc.String())
-		}
-
-		for _, runnerLabel := range job.RunsOn() {
-			platformName := rc.ExprEval.Interpolate(ctx, runnerLabel)
 			l.Infof("\U0001F6A7  Skipping unsupported platform -- Try running with `-P %+v=...`", platformName)
 		}
 		return false, nil
@@ -923,9 +927,7 @@ func (rc *RunContext) withGithubEnv(ctx context.Context, github *model.GithubCon
 		setActionRuntimeVars(rc, env)
 	}
 
-	job := rc.Run.Job()
+	for _, platformName := range rc.runsOnPlatformNames(ctx) {
-	for _, runnerLabel := range job.RunsOn() {
-		platformName := rc.ExprEval.Interpolate(ctx, runnerLabel)
 		if platformName != "" {
 			if platformName == "ubuntu-latest" {
 				// hardcode current ubuntu-latest since we have no way to check that 'on the fly'

pkg/runner/run_context_test.go

@@ -470,6 +470,53 @@ func createJob(t *testing.T, input string, result string) *model.Job {
 	return job
 }
 
+func TestRunContextRunsOnPlatformNames(t *testing.T) {
+	log.SetLevel(log.DebugLevel)
+	assertObject := assert.New(t)
+
+	rc := createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: ubuntu-latest`, ""),
+	})
+	assertObject.Equal([]string{"ubuntu-latest"}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: ${{ 'ubuntu-latest' }}`, ""),
+	})
+	assertObject.Equal([]string{"ubuntu-latest"}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: [self-hosted, my-runner]`, ""),
+	})
+	assertObject.Equal([]string{"self-hosted", "my-runner"}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: [self-hosted, "${{ 'my-runner' }}"]`, ""),
+	})
+	assertObject.Equal([]string{"self-hosted", "my-runner"}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: ${{ fromJSON('["ubuntu-latest"]') }}`, ""),
+	})
+	assertObject.Equal([]string{"ubuntu-latest"}, rc.runsOnPlatformNames(context.Background()))
+
+	// test missing / invalid runs-on
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `name: something`, ""),
+	})
+	assertObject.Equal([]string{}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on:
+  mapping: value`, ""),
+	})
+	assertObject.Equal([]string{}, rc.runsOnPlatformNames(context.Background()))
+
+	rc = createIfTestRunContext(map[string]*model.Job{
+		"job1": createJob(t, `runs-on: ${{ invalid expression }}`, ""),
+	})
+	assertObject.Equal([]string{}, rc.runsOnPlatformNames(context.Background()))
+}
+
 func TestRunContextIsEnabled(t *testing.T) {
 	log.SetLevel(log.DebugLevel)
 	assertObject := assert.New(t)