Add --watch-chdir flag

README.md

@@ -358,6 +358,12 @@ packages as command line arguments (ex: `gotestsum --watch -- ./...` or
 `gotestsum --watch -- ./extrapkg`), the
 tests in those packages will also be run when any file changes.
 
+With the `--watch-chdir` flag, `gotestsum` will change the working directory
+to the directory with the modified file before running tests. Changing the
+directory is primarily useful when the project contains multiple Go modules.
+Without this flag, `go test` will refuse to run tests for any package outside
+of the main Go module.
+
 While in watch mode, pressing some keys will perform an action:
 
 * `r` will run tests for the previous event.

cmd/main.go

@@ -78,6 +78,8 @@ func setupFlags(name string) (*pflag.FlagSet, *options) {
 		"command to run after the tests have completed")
 	flags.BoolVar(&opts.watch, "watch", false,
 		"watch go files, and run tests when a file is modified")
+	flags.BoolVar(&opts.watchChdir, "watch-chdir", false,
+		"in watch mode change the working directory to the directory with the modified file before running tests")
 	flags.IntVar(&opts.maxFails, "max-fails", 0,
 		"end the test run after this number of failures")
 
@@ -93,7 +95,7 @@ func setupFlags(name string) (*pflag.FlagSet, *options) {
 		"name of the project used in the junit.xml file")
 
 	flags.IntVar(&opts.rerunFailsMaxAttempts, "rerun-fails", 0,
-		"rerun failed tests until they all pass, or attempts exceeds maximum. Defaults to max 2 reruns when enabled.")
+		"rerun failed tests until they all pass, or attempts exceeds maximum. Defaults to max 2 reruns when enabled")
 	flags.Lookup("rerun-fails").NoOptDefVal = "2"
 	flags.IntVar(&opts.rerunFailsMaxInitialFailures, "rerun-fails-max-failures", 10,
 		"do not rerun any tests if the initial run has more than this number of failures")
@@ -163,6 +165,7 @@ type options struct {
 	rerunFailsRunRootCases       bool
 	packages                     []string
 	watch                        bool
+	watchChdir                   bool
 	maxFails                     int
 	version                      bool
 
@@ -202,7 +205,7 @@ func run(opts *options) error {
 		return err
 	}
 
-	goTestProc, err := startGoTestFn(ctx, goTestCmdArgs(opts, rerunOpts{}))
+	goTestProc, err := startGoTestFn(ctx, "", goTestCmdArgs(opts, rerunOpts{}))
 	if err != nil {
 		return err
 	}
@@ -362,13 +365,15 @@ type waiter interface {
 	Wait() error
 }
 
-func startGoTest(ctx context.Context, args []string) (*proc, error) {
+func startGoTest(ctx context.Context, dir string, args []string) (*proc, error) {
 	if len(args) == 0 {
 		return nil, errors.New("missing command to run")
 	}
 
 	cmd := exec.CommandContext(ctx, args[0], args[1:]...)
 	cmd.Stdin = os.Stdin
+	cmd.Dir = dir
+
 	p := proc{cmd: cmd}
 	log.Debugf("exec: %s", cmd.Args)
 	var err error

cmd/rerunfails.go

@@ -61,7 +61,7 @@ func rerunFailed(ctx context.Context, opts *options, scanConfig testjson.ScanCon
 
 		nextRec := newFailureRecorder(scanConfig.Handler)
 		for _, tc := range tcFilter(rec.failures) {
-			goTestProc, err := startGoTestFn(ctx, goTestCmdArgs(opts, newRerunOptsFromTestCase(tc)))
+			goTestProc, err := startGoTestFn(ctx, "", goTestCmdArgs(opts, newRerunOptsFromTestCase(tc)))
 			if err != nil {
 				return err
 			}

cmd/rerunfails_test.go

@@ -138,7 +138,7 @@ func TestRerunFailed_ReturnsAnErrorWhenTheLastTestIsSuccessful(t *testing.T) {
 
 func patchStartGoTestFn(f func(args []string) *proc) func() {
 	orig := startGoTestFn
-	startGoTestFn = func(ctx context.Context, args []string) (*proc, error) {
+	startGoTestFn = func(ctx context.Context, dir string, args []string) (*proc, error) {
 		return f(args), nil
 	}
 	return func() {

cmd/testdata/gotestsum-help-text

@@ -18,12 +18,13 @@ Flags:
       --packages list                               space separated list of package to test
       --post-run-command command                    command to run after the tests have completed
       --raw-command                                 don't prepend 'go test -json' to the 'go test' command
-      --rerun-fails int[=2]                         rerun failed tests until they all pass, or attempts exceeds maximum. Defaults to max 2 reruns when enabled.
+      --rerun-fails int[=2]                         rerun failed tests until they all pass, or attempts exceeds maximum. Defaults to max 2 reruns when enabled
       --rerun-fails-max-failures int                do not rerun any tests if the initial run has more than this number of failures (default 10)
       --rerun-fails-report string                   write a report to the file, of the tests that were rerun
       --rerun-fails-run-root-test                   rerun the entire root testcase when any of its subtests fail, instead of only the failed subtest
       --version                                     show version and exit
       --watch                                       watch go files, and run tests when a file is modified
+      --watch-chdir                                 in watch mode change the working directory to the directory with the modified file before running tests
 
 Formats:
     dots                     print a character for each test

cmd/watch.go

@@ -43,13 +43,18 @@ func (w *watchRuns) run(event filewatcher.Event) error {
 		return nil
 	}
 
+	var dir string
+	if w.opts.watchChdir {
+		dir, event.PkgPath = event.PkgPath, "./"
+	}
+
 	opts := w.opts // shallow copy opts
 	opts.packages = append([]string{}, opts.packages...)
 	opts.packages = append(opts.packages, event.PkgPath)
 	opts.packages = append(opts.packages, event.Args...)
 
 	var err error
-	if w.prevExec, err = runSingle(&opts); !IsExitCoder(err) {
+	if w.prevExec, err = runSingle(&opts, dir); !IsExitCoder(err) {
 		return err
 	}
 	return nil
@@ -58,15 +63,15 @@ func (w *watchRuns) run(event filewatcher.Event) error {
 // runSingle is similar to run. It doesn't support rerun-fails. It may be
 // possible to share runSingle with run, but the defer close on the handler
 // would require at least 3 return values, so for now it is a copy.
-func runSingle(opts *options) (*testjson.Execution, error) {
+func runSingle(opts *options, dir string) (*testjson.Execution, error) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
 	if err := opts.Validate(); err != nil {
 		return nil, err
 	}
 
-	goTestProc, err := startGoTestFn(ctx, goTestCmdArgs(opts, rerunOpts{}))
+	goTestProc, err := startGoTestFn(ctx, dir, goTestCmdArgs(opts, rerunOpts{}))
 	if err != nil {
 		return nil, err
 	}