require "experimentalDecorators": true (#104)

CHANGELOG.md

@@ -6,6 +6,10 @@
 
     This release makes the following changes to esbuild's `tsconfig.json` support:
 
+    * Using experimental decorators now requires `"experimentalDecorators": true` ([#104](https://github.com/evanw/esbuild/issues/104))
+
+        Previously esbuild would always compile decorators in TypeScript code using TypeScript's experimental decorator transform. Now that standard JavaScript decorators are close to being finalized, esbuild will now require you to use `"experimentalDecorators": true` to do this. This new requirement makes it possible for esbuild to introduce a transform for standard JavaScript decorators in TypeScript code in the future. Such a transform has not been implemented yet, however.
+
     * TypeScript's `target` no longer affects esbuild's `target` ([#2628](https://github.com/evanw/esbuild/issues/2628))
 
         Some people requested that esbuild support TypeScript's `target` setting, so support for it was added (in [version 0.12.4](https://github.com/evanw/esbuild/releases/v0.12.4)). However, esbuild supports reading from multiple `tsconfig.json` files within a single build, which opens up the possibility that different files in the build have different language targets configured. There isn't really any reason to do this and it can lead to unexpected results. So with this release, the `target` setting in `tsconfig.json` will no longer affect esbuild's own `target` setting. You will have to use esbuild's own target setting instead (which is a single, global value).

internal/bundler_tests/bundler_ts_test.go

@@ -803,6 +803,30 @@ func TestTSMinifiedBundleCommonJS(t *testing.T) {
 	})
 }
 
+func TestTSExperimentalDecoratorsNoConfig(t *testing.T) {
+	ts_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.ts": `
+				@decorator
+				class Foo {}
+			`,
+			"/tsconfig.json": `{
+				"compilerOptions": {
+					"experimentalDecorators": false
+				}
+			}`,
+		},
+		entryPaths: []string{"/entry.ts"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			AbsOutputFile: "/out.js",
+		},
+		expectedScanLog: "entry.ts: ERROR: Experimental decorators are not currently enabled\n" +
+			"NOTE: To use experimental decorators in TypeScript with esbuild, you need to enable them by adding \"experimentalDecorators\": true in your \"tsconfig.json\" file. " +
+			"TypeScript's experimental decorators are currently the only kind of decorators that esbuild supports.\n",
+	})
+}
+
 func TestTSExperimentalDecorators(t *testing.T) {
 	ts_suite.expectBundled(t, bundled{
 		files: map[string]string{
@@ -942,7 +966,8 @@ func TestTSExperimentalDecorators(t *testing.T) {
 			`,
 			"/tsconfig.json": `{
 				"compilerOptions": {
-					"useDefineForClassFields": false
+					"useDefineForClassFields": false,
+					"experimentalDecorators": true
 				}
 			}`,
 		},
@@ -961,6 +986,11 @@ func TestTSExperimentalDecoratorsKeepNames(t *testing.T) {
 				@decoratorMustComeAfterName
 				class Foo {}
 			`,
+			"/tsconfig.json": `{
+				"compilerOptions": {
+					"experimentalDecorators": true
+				}
+			}`,
 		},
 		entryPaths: []string{"/entry.ts"},
 		options: config.Options{
@@ -1001,7 +1031,8 @@ func TestTSExperimentalDecoratorScopeIssue2147(t *testing.T) {
 			`,
 			"/tsconfig.json": `{
 				"compilerOptions": {
-					"useDefineForClassFields": false
+					"useDefineForClassFields": false,
+					"experimentalDecorators": true
 				}
 			}`,
 		},
@@ -1439,14 +1470,17 @@ func TestTSComputedClassFieldUseDefineFalse(t *testing.T) {
 				}
 				new Foo()
 			`,
+			"/tsconfig.json": `{
+				"compilerOptions": {
+					"useDefineForClassFields": false,
+					"experimentalDecorators": true
+				}
+			}`,
 		},
 		entryPaths: []string{"/entry.ts"},
 		options: config.Options{
 			Mode:          config.ModePassThrough,
 			AbsOutputFile: "/out.js",
-			TS: config.TSOptions{Config: config.TSConfig{
-				UseDefineForClassFields: config.False,
-			}},
 		},
 	})
 }
@@ -1465,14 +1499,17 @@ func TestTSComputedClassFieldUseDefineTrue(t *testing.T) {
 				}
 				new Foo()
 			`,
+			"/tsconfig.json": `{
+				"compilerOptions": {
+					"useDefineForClassFields": true,
+					"experimentalDecorators": true
+				}
+			}`,
 		},
 		entryPaths: []string{"/entry.ts"},
 		options: config.Options{
 			Mode:          config.ModePassThrough,
 			AbsOutputFile: "/out.js",
-			TS: config.TSOptions{Config: config.TSConfig{
-				UseDefineForClassFields: config.True,
-			}},
 		},
 	})
 }
@@ -1491,14 +1528,17 @@ func TestTSComputedClassFieldUseDefineTrueLower(t *testing.T) {
 				}
 				new Foo()
 			`,
+			"/tsconfig.json": `{
+				"compilerOptions": {
+					"useDefineForClassFields": true,
+					"experimentalDecorators": true
+				}
+			}`,
 		},
 		entryPaths: []string{"/entry.ts"},
 		options: config.Options{
-			Mode:          config.ModePassThrough,
-			AbsOutputFile: "/out.js",
-			TS: config.TSOptions{Config: config.TSConfig{
-				UseDefineForClassFields: config.True,
-			}},
+			Mode:                  config.ModePassThrough,
+			AbsOutputFile:         "/out.js",
 			UnsupportedJSFeatures: compat.ClassField,
 		},
 	})

internal/config/config.go

@@ -83,6 +83,7 @@ type TSConfigJSX struct {
 // Note: This can currently only contain primitive values. It's compared
 // for equality using a structural equality comparison by the JS parser.
 type TSConfig struct {
+	ExperimentalDecorators  MaybeBool
 	ImportsNotUsedAsValues  TSImportsNotUsedAsValues
 	PreserveValueImports    MaybeBool
 	Target                  TSTarget

internal/js_parser/js_parser.go

@@ -6259,6 +6259,11 @@ func (p *parser) parseDecorators(decoratorScope *js_ast.Scope, classKeyword logg
 					[]logger.MsgData{p.tracker.MsgData(classKeyword, "This is a class expression, not a class declaration:")})
 			} else if (context & decoratorBeforeClassExpr) != 0 {
 				p.log.AddError(&p.tracker, p.lexer.Range(), "Experimental decorators cannot be used in expression position in TypeScript")
+			} else if p.options.ts.Config.ExperimentalDecorators != config.True {
+				p.log.AddErrorWithNotes(&p.tracker, p.lexer.Range(), "Experimental decorators are not currently enabled", []logger.MsgData{{
+					Text: "To use experimental decorators in TypeScript with esbuild, you need to enable them by adding \"experimentalDecorators\": true in your \"tsconfig.json\" file. " +
+						"TypeScript's experimental decorators are currently the only kind of decorators that esbuild supports.",
+				}})
 			}
 		} else {
 			if (context & decoratorInFnArgs) != 0 {