dawn_node: Run CTS serially if --j 0 is specified

Spinning up new devices for each test can take a long time.
Specifying --j 0 will run a single instance of node, with the given query to run.

Change-Id: I27c161bb76f5deaaa505ab5ae361ea6a0942a130
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/66880
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

src/dawn_node/tools/src/cmd/run-cts/main.go

@@ -16,6 +16,7 @@
 package main
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -78,7 +79,7 @@ func run() error {
 	flag.BoolVar(&verbose, "verbose", false, "print extra information while testing")
 	flag.BoolVar(&build, "build", true, "attempt to build the CTS before running")
 	flag.BoolVar(&colors, "colors", colors, "enable / disable colors")
-	flag.IntVar(&numRunners, "j", runtime.NumCPU(), "number of concurrent runners")
+	flag.IntVar(&numRunners, "j", runtime.NumCPU(), "number of concurrent runners. 0 runs serially")
 	flag.StringVar(&logFilename, "log", "", "path to log file of tests run and result")
 	flag.Parse()
 
@@ -109,9 +110,13 @@ func run() error {
 	}
 
 	// The test query is the optional unnamed argument
-	queries := []string{"webgpu:*"}
-	if args := flag.Args(); len(args) > 0 {
-		queries = args
+	query := "webgpu:*"
+	switch len(flag.Args()) {
+	case 0:
+	case 1:
+		query = flag.Args()[0]
+	default:
+		return fmt.Errorf("only a single query can be provided")
 	}
 
 	// Find node
@@ -184,14 +189,18 @@ func run() error {
 		}
 	}
 
+	if numRunners > 0 {
 		// Find all the test cases that match the given queries.
-	if err := r.gatherTestCases(queries, verbose); err != nil {
+		if err := r.gatherTestCases(query, verbose); err != nil {
 			return fmt.Errorf("failed to gather test cases: %w", err)
 		}
 
 		fmt.Printf("Testing %d test cases...\n", len(r.testcases))
+		return r.runParallel()
+	}
 
-	return r.run()
+	fmt.Println("Running serially...")
+	return r.runSerially(query)
 }
 
 type logger struct {
@@ -308,7 +317,7 @@ func (r *runner) buildCTS(verbose bool) error {
 
 // gatherTestCases() queries the CTS for all test cases that match the given
 // query. On success, gatherTestCases() populates r.testcases.
-func (r *runner) gatherTestCases(queries []string, verbose bool) error {
+func (r *runner) gatherTestCases(query string, verbose bool) error {
 	if verbose {
 		start := time.Now()
 		fmt.Println("Gathering test cases...")
@@ -325,7 +334,7 @@ func (r *runner) gatherTestCases(queries []string, verbose bool) error {
 		// start at 1, so just inject a dummy argument.
 		"dummy-arg",
 		"--list",
-	}, queries...)
+	}, query)
 
 	cmd := exec.Command(r.node, args...)
 	cmd.Dir = r.cts
@@ -339,9 +348,10 @@ func (r *runner) gatherTestCases(queries []string, verbose bool) error {
 	return nil
 }
 
-// run() calls the CTS test runner to run each testcase in a separate process.
+// runParallel() calls the CTS test runner to run each testcase in a separate
+// process.
 // Up to r.numRunners tests will be run concurrently.
-func (r *runner) run() error {
+func (r *runner) runParallel() error {
 	// Create a chan of test indices.
 	// This will be read by the test runner goroutines.
 	caseIndices := make(chan int, len(r.testcases))
@@ -362,7 +372,9 @@ func (r *runner) run() error {
 		go func() {
 			defer wg.Done()
 			for idx := range caseIndices {
-				results <- r.runTestcase(idx)
+				res := r.runTestcase(r.testcases[idx], false)
+				res.index = idx
+				results <- res
 			}
 		}()
 	}
@@ -429,6 +441,18 @@ timeout: %v (%v)
 	return nil
 }
 
+// runSerially() calls the CTS test runner to run the test query in a single
+// process.
+func (r *runner) runSerially(query string) error {
+	start := time.Now()
+	result := r.runTestcase(query, true)
+	timeTaken := time.Since(start)
+
+	fmt.Println("Completed in", timeTaken)
+	fmt.Println(result)
+	return nil
+}
+
 // status is an enumerator of test result status
 type status string
 
@@ -448,14 +472,12 @@ type result struct {
 	error    error
 }
 
-// runTestcase() runs the CTS testcase with the given index, returning the test
+// runTestcase() runs the CTS testcase with the given query, returning the test
 // result.
-func (r *runner) runTestcase(idx int) result {
+func (r *runner) runTestcase(query string, printToStout bool) result {
 	ctx, cancel := context.WithTimeout(context.Background(), testTimeout)
 	defer cancel()
 
-	testcase := r.testcases[idx]
-
 	eval := r.evalScript
 	args := append([]string{
 		"-e", eval, // Evaluate 'eval'.
@@ -467,23 +489,33 @@ func (r *runner) runTestcase(idx int) result {
 		// Actual arguments begin here
 		"--gpu-provider", r.dawnNode,
 		"--verbose",
-	}, testcase)
+	}, query)
 
 	cmd := exec.CommandContext(ctx, r.node, args...)
 	cmd.Dir = r.cts
-	out, err := cmd.CombinedOutput()
-	msg := string(out)
+
+	var buf bytes.Buffer
+	if printToStout {
+		cmd.Stdout = io.MultiWriter(&buf, os.Stdout)
+		cmd.Stderr = io.MultiWriter(&buf, os.Stderr)
+	} else {
+		cmd.Stdout = &buf
+		cmd.Stderr = &buf
+	}
+
+	err := cmd.Run()
+	msg := buf.String()
 	switch {
 	case errors.Is(err, context.DeadlineExceeded):
-		return result{index: idx, testcase: testcase, status: timeout, message: msg}
+		return result{testcase: query, status: timeout, message: msg}
 	case strings.Contains(msg, "[fail]"):
-		return result{index: idx, testcase: testcase, status: fail, message: msg}
+		return result{testcase: query, status: fail, message: msg}
 	case strings.Contains(msg, "[skip]"):
-		return result{index: idx, testcase: testcase, status: skip, message: msg}
+		return result{testcase: query, status: skip, message: msg}
 	case strings.Contains(msg, "[pass]"), err == nil:
-		return result{index: idx, testcase: testcase, status: pass, message: msg}
+		return result{testcase: query, status: pass, message: msg}
 	}
-	return result{index: idx, testcase: testcase, status: fail, message: fmt.Sprint(msg, err), error: err}
+	return result{testcase: query, status: fail, message: fmt.Sprint(msg, err), error: err}
 }
 
 // filterTestcases returns in with empty strings removed