fix service deadlock after failed build setup (#4506)

cmd/esbuild/service.go

@@ -639,6 +639,12 @@ func (service *serviceType) handleBuildRequest(id uint32, request map[string]int
 	}
 
 	activeBuild := service.createActiveBuild(key)
+	shouldDestroyActiveBuild := true
+	defer func() {
+		if shouldDestroyActiveBuild {
+			service.destroyActiveBuild(key)
+		}
+	}()
 
 	hasOnEndCallbacks := false
 	if plugins, ok := request["plugins"]; ok {
@@ -769,6 +775,7 @@ func (service *serviceType) handleBuildRequest(id uint32, request map[string]int
 		// Keep the build alive until "dispose" has been called
 		activeBuild.disposeWaitGroup.Add(1)
 		activeBuild.ctx = ctx
+		shouldDestroyActiveBuild = false
 
 		return encodePacket(packet{
 			id: id,
@@ -782,8 +789,6 @@ func (service *serviceType) handleBuildRequest(id uint32, request map[string]int
 	result := api.Build(options)
 	response := resultToResponse(result)
 
-	service.destroyActiveBuild(key)
-
 	return encodePacket(packet{
 		id:    id,
 		value: response,

cmd/esbuild/service_test.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/evanw/esbuild/internal/helpers"
+)
+
+func TestHandleBuildRequestReleasesActiveBuildAfterError(t *testing.T) {
+	absWorkingDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tests := []struct {
+		name            string
+		modifyRequest   func(map[string]interface{})
+		expectedError   string
+		expectedMessage string
+	}{
+		{
+			name: "InvalidPluginRegExp",
+			modifyRequest: func(request map[string]interface{}) {
+				request["plugins"] = []interface{}{map[string]interface{}{
+					"name":  "test",
+					"onEnd": false,
+					"onResolve": []interface{}{map[string]interface{}{
+						"id":        0,
+						"filter":    "x(?=y)",
+						"namespace": "",
+					}},
+					"onLoad": []interface{}{},
+				}}
+			},
+			expectedError: "[test] \"onResolve\" filter is not a valid Go regular expression: \"x(?=y)\"",
+		},
+		{
+			name: "InvalidContextOptions",
+			modifyRequest: func(request map[string]interface{}) {
+				request["context"] = true
+				request["flags"] = []interface{}{"--external:test"}
+			},
+			expectedMessage: "Cannot use \"external\" without \"bundle\"",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			service := serviceType{
+				activeBuilds:       make(map[int]*activeBuild),
+				keepAliveWaitGroup: helpers.MakeThreadSafeWaitGroup(),
+			}
+			request := map[string]interface{}{
+				"context":       false,
+				"key":           0,
+				"write":         false,
+				"entries":       []interface{}{},
+				"flags":         []interface{}{},
+				"absWorkingDir": absWorkingDir,
+				"nodePaths":     []interface{}{},
+			}
+			test.modifyRequest(request)
+
+			encoded := service.handleBuildRequest(0, request)
+			bytes, _, ok := readLengthPrefixedSlice(encoded)
+			if !ok {
+				t.Fatal("Invalid encoded response")
+			}
+			response, ok := decodePacket(bytes)
+			if !ok {
+				t.Fatal("Invalid response packet")
+			}
+			value := response.value.(map[string]interface{})
+			if test.expectedError != "" && value["error"] != test.expectedError {
+				t.Fatalf("Expected error %q, got %q", test.expectedError, value["error"])
+			}
+			if test.expectedMessage != "" {
+				errors := value["errors"].([]interface{})
+				if len(errors) != 1 || errors[0].(map[string]interface{})["text"] != test.expectedMessage {
+					t.Fatalf("Expected message %q, got %v", test.expectedMessage, errors)
+				}
+			}
+
+			if service.getActiveBuild(0) != nil {
+				t.Fatal("Active build was not released")
+			}
+
+			done := make(chan struct{})
+			go func() {
+				service.keepAliveWaitGroup.Wait()
+				close(done)
+			}()
+			select {
+			case <-done:
+			case <-time.After(time.Second):
+				t.Fatal("Keep-alive wait group did not reach zero")
+			}
+		})
+	}
+}