service/dap: add go build stderr to error response (#2448)

* service/dap: add go build stderr to error response

* service/dap: add go build stderr to error response

* Skip message check for build errors

* test for flag provided message

pkg/gobuild/gobuild.go

@@ -54,32 +54,58 @@ func optflags(args []string) []string {
 // GoBuild builds non-test files in 'pkgs' with the specified 'buildflags'
 // and writes the output at 'debugname'.
 func GoBuild(debugname string, pkgs []string, buildflags string) error {
-	args := []string{"-o", debugname}
+	args := goBuildArgs(debugname, pkgs, buildflags, false)
-	args = optflags(args)
+	return gocommandRun("build", args...)
-	if buildflags != "" {
-		args = append(args, config.SplitQuotedFields(buildflags, '\'')...)
-	}
-	args = append(args, pkgs...)
-	return gocommand("build", args...)
 }
 
-// GoBuild builds test files 'pkgs' with the specified 'buildflags'
+// GoBuildCombinedOutput builds non-test files in 'pkgs' with the specified 'buildflags'
+// and writes the output at 'debugname'.
+func GoBuildCombinedOutput(debugname string, pkgs []string, buildflags string) ([]byte, error) {
+	args := goBuildArgs(debugname, pkgs, buildflags, false)
+	return gocommandCombinedOutput("build", args...)
+}
+
+// GoTestBuild builds test files 'pkgs' with the specified 'buildflags'
 // and writes the output at 'debugname'.
 func GoTestBuild(debugname string, pkgs []string, buildflags string) error {
-	args := []string{"-c", "-o", debugname}
+	args := goBuildArgs(debugname, pkgs, buildflags, true)
+	return gocommandRun("test", args...)
+}
+
+// GoTestBuildCombinedOutput builds test files 'pkgs' with the specified 'buildflags'
+// and writes the output at 'debugname'.
+func GoTestBuildCombinedOutput(debugname string, pkgs []string, buildflags string) ([]byte, error) {
+	args := goBuildArgs(debugname, pkgs, buildflags, true)
+	return gocommandCombinedOutput("test", args...)
+}
+
+func goBuildArgs(debugname string, pkgs []string, buildflags string, isTest bool) []string {
+	args := []string{"-o", debugname}
+	if isTest {
+		args = append([]string{"-c"}, args...)
+	}
 	args = optflags(args)
 	if buildflags != "" {
 		args = append(args, config.SplitQuotedFields(buildflags, '\'')...)
 	}
 	args = append(args, pkgs...)
-	return gocommand("test", args...)
+	return args
 }
 
-func gocommand(command string, args ...string) error {
+func gocommandRun(command string, args ...string) error {
+	goBuild := gocommandExecCmd(command, args...)
+	goBuild.Stderr = os.Stdout
+	goBuild.Stdout = os.Stderr
+	return goBuild.Run()
+}
+
+func gocommandCombinedOutput(command string, args ...string) ([]byte, error) {
+	return gocommandExecCmd(command, args...).CombinedOutput()
+}
+
+func gocommandExecCmd(command string, args ...string) *exec.Cmd {
 	allargs := []string{command}
 	allargs = append(allargs, args...)
 	goBuild := exec.Command("go", allargs...)
-	goBuild.Stderr = os.Stderr
+	return goBuild
-	goBuild.Stdout = os.Stdout
-	return goBuild.Run()
 }

service/dap/server.go

@@ -566,16 +566,17 @@ func (s *Server) onLaunchRequest(request *dap.LaunchRequest) {
 		}
 
 		s.log.Debugf("building binary at %s", debugbinary)
+		var out []byte
 		switch mode {
 		case "debug":
-			err = gobuild.GoBuild(debugbinary, []string{program}, buildFlags)
+			out, err = gobuild.GoBuildCombinedOutput(debugbinary, []string{program}, buildFlags)
 		case "test":
-			err = gobuild.GoTestBuild(debugbinary, []string{program}, buildFlags)
+			out, err = gobuild.GoTestBuildCombinedOutput(debugbinary, []string{program}, buildFlags)
 		}
 		if err != nil {
 			s.sendErrorResponse(request.Request,
 				FailedToLaunch, "Failed to launch",
-				fmt.Sprintf("Build error: %s", err.Error()))
+				fmt.Sprintf("Build error: %s (%s)", strings.TrimSpace(string(out)), err.Error()))
 			return
 		}
 		program = debugbinary

service/dap/server_test.go

@@ -2999,6 +2999,14 @@ func TestBadLaunchRequests(t *testing.T) {
 			}
 		}
 
+		expectFailedToLaunchWithMessageRegex := func(response *dap.ErrorResponse, errmsg string) {
+			t.Helper()
+			expectFailedToLaunch(response)
+			if matched, _ := regexp.MatchString(errmsg, response.Body.Error.Format); !matched {
+				t.Errorf("\ngot  %q\nwant %q", response.Body.Error.Format, errmsg)
+			}
+		}
+
 		// Test for the DAP-specific detailed error message.
 		client.LaunchRequest("exec", "", stopOnEntry)
 		expectFailedToLaunchWithMessage(client.ExpectErrorResponse(t),
@@ -3080,18 +3088,18 @@ func TestBadLaunchRequests(t *testing.T) {
 		expectFailedToLaunch(client.ExpectErrorResponse(t)) // No such file or directory
 
 		client.LaunchRequest("debug", fixture.Path+"_does_not_exist", stopOnEntry)
-		expectFailedToLaunchWithMessage(client.ExpectErrorResponse(t), "Failed to launch: Build error: exit status 1")
+		expectFailedToLaunch(client.ExpectErrorResponse(t))
 
 		client.LaunchRequest("" /*debug by default*/, fixture.Path+"_does_not_exist", stopOnEntry)
-		expectFailedToLaunchWithMessage(client.ExpectErrorResponse(t), "Failed to launch: Build error: exit status 1")
+		expectFailedToLaunch(client.ExpectErrorResponse(t))
 
 		client.LaunchRequest("exec", fixture.Source, stopOnEntry)
 		expectFailedToLaunch(client.ExpectErrorResponse(t)) // Not an executable
 
-		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "buildFlags": "bad flags"})
+		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "buildFlags": "-bad -flags"})
-		expectFailedToLaunchWithMessage(client.ExpectErrorResponse(t), "Failed to launch: Build error: exit status 1")
+		expectFailedToLaunchWithMessageRegex(client.ExpectErrorResponse(t), `Failed to launch: Build error: .*flag provided but not defined.*`)
-		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "noDebug": true, "buildFlags": "bad flags"})
+		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "noDebug": true, "buildFlags": "-bad -flags"})
-		expectFailedToLaunchWithMessage(client.ExpectErrorResponse(t), "Failed to launch: Build error: exit status 1")
+		expectFailedToLaunchWithMessageRegex(client.ExpectErrorResponse(t), `Failed to launch: Build error: .*flag provided but not defined.*`)
 
 		// Bad "wd".
 		client.LaunchRequestWithArgs(map[string]interface{}{"mode": "debug", "program": fixture.Source, "noDebug": false, "cwd": "dir/invalid"})