fix #975: add target env to lowering error

CHANGELOG.md

@@ -48,6 +48,10 @@
 
     However, some features can have subtests that each check a different aspect of the feature. In this case the desired version is the minimum version within each individual subtest, but the maximum of those versions across all subtests (since esbuild should only use the feature if it works in all cases). Previously esbuild computed the minimum version across all subtests, but now esbuild computes the maximum version across all subtests. This means esbuild will now lower JavaScript syntax in more cases.
 
+* Mention the configured target environment in error messages ([#975](https://github.com/evanw/esbuild/issues/975))
+
+    Using newer JavaScript syntax with an older target environment (e.g. `chrome10`) can cause a build error if esbuild doesn't support transforming that syntax such that it is compatible with that target environment. Previously the error message was generic but with this release, the target environment is called outp explicitly in the error message. This is helpful if esbuild is being wrapped by some other tool since the other tool can obscure what target environment is actually being passed to esbuild.
+
 ## 0.9.2
 
 * Fix export name annotations in CommonJS output for node ([#960](https://github.com/evanw/esbuild/issues/960))

internal/compat/js_table.go

@@ -14,6 +14,26 @@ const (
 	Safari
 )
 
+func (e Engine) String() string {
+	switch e {
+	case Chrome:
+		return "chrome"
+	case Edge:
+		return "edge"
+	case ES:
+		return "es"
+	case Firefox:
+		return "firefox"
+	case IOS:
+		return "ios"
+	case Node:
+		return "node"
+	case Safari:
+		return "safari"
+	}
+	return ""
+}
+
 type JSFeature uint64
 
 const (

internal/config/config.go

@@ -199,6 +199,10 @@ type Options struct {
 	UnsupportedJSFeatures  compat.JSFeature
 	UnsupportedCSSFeatures compat.CSSFeature
 
+	// This is the original information that was used to generate the
+	// unsupported feature sets above. It's used for error messages.
+	OriginalTargetEnv string
+
 	ExtensionOrder  []string
 	MainFields      []string
 	Conditions      []string

internal/js_parser/js_parser.go

@@ -280,6 +280,7 @@ type Options struct {
 
 type optionsThatSupportStructuralEquality struct {
 	unsupportedJSFeatures compat.JSFeature
+	originalTargetEnv     string
 
 	// Byte-sized values go here (gathered together here to keep this object compact)
 	ts                             config.TSOptions
@@ -304,6 +305,7 @@ func OptionsFromConfig(options *config.Options) Options {
 		defines:       options.Defines,
 		optionsThatSupportStructuralEquality: optionsThatSupportStructuralEquality{
 			unsupportedJSFeatures:          options.UnsupportedJSFeatures,
+			originalTargetEnv:              options.OriginalTargetEnv,
 			ts:                             options.TS,
 			mode:                           options.Mode,
 			platform:                       options.Platform,

internal/js_parser/js_parser_lower.go

@@ -37,6 +37,10 @@ func (p *parser) markSyntaxFeature(feature compat.JSFeature, r logger.Range) (di
 	var name string
 	where := "the configured target environment"
 
+	if p.options.originalTargetEnv != "" {
+		where = fmt.Sprintf("%s (%s)", where, p.options.originalTargetEnv)
+	}
+
 	switch feature {
 	case compat.DefaultArgument:
 		name = "default arguments"

pkg/api/api_impl.go

@@ -233,8 +233,9 @@ func validateEngine(value EngineName) compat.Engine {
 
 var versionRegex = regexp.MustCompile(`^([0-9]+)(?:\.([0-9]+))?(?:\.([0-9]+))?$`)
 
-func validateFeatures(log logger.Log, target Target, engines []Engine) (compat.JSFeature, compat.CSSFeature) {
+func validateFeatures(log logger.Log, target Target, engines []Engine) (compat.JSFeature, compat.CSSFeature, string) {
 	constraints := make(map[compat.Engine][]int)
+	targets := make([]string, 0, 1+len(engines))
 
 	switch target {
 	case ES5:
@@ -289,7 +290,23 @@ func validateFeatures(log logger.Log, target Target, engines []Engine) (compat.J
 		log.AddError(nil, logger.Loc{}, fmt.Sprintf("Invalid version: %q", engine.Version))
 	}
 
-	return compat.UnsupportedJSFeatures(constraints), compat.UnsupportedCSSFeatures(constraints)
+	for engine, version := range constraints {
+		var text string
+		switch len(version) {
+		case 1:
+			text = fmt.Sprintf("%s%d", engine.String(), version[0])
+		case 2:
+			text = fmt.Sprintf("%s%d.%d", engine.String(), version[0], version[1])
+		case 3:
+			text = fmt.Sprintf("%s%d.%d.%d", engine.String(), version[0], version[1], version[2])
+		}
+		targets = append(targets, fmt.Sprintf("%q", text))
+	}
+
+	sort.Strings(targets)
+	targetEnv := strings.Join(targets, ", ")
+
+	return compat.UnsupportedJSFeatures(constraints), compat.UnsupportedCSSFeatures(constraints), targetEnv
 }
 
 func validateGlobalName(log logger.Log, text string) []string {
@@ -699,14 +716,15 @@ func rebuildImpl(
 		// This should already have been checked above
 		panic(err.Error())
 	}
-	jsFeatures, cssFeatures := validateFeatures(log, buildOpts.Target, buildOpts.Engines)
+	jsFeatures, cssFeatures, targetEnv := validateFeatures(log, buildOpts.Target, buildOpts.Engines)
 	outJS, outCSS := validateOutputExtensions(log, buildOpts.OutExtensions)
 	bannerJS, bannerCSS := validateBannerOrFooter(log, "banner", buildOpts.Banner)
 	footerJS, footerCSS := validateBannerOrFooter(log, "footer", buildOpts.Footer)
 	defines, injectedDefines := validateDefines(log, buildOpts.Define, buildOpts.Pure)
 	options := config.Options{
 		UnsupportedJSFeatures:  jsFeatures,
 		UnsupportedCSSFeatures: cssFeatures,
+		OriginalTargetEnv:      targetEnv,
 		JSX: config.JSXOptions{
 			Factory:  validateJSX(log, buildOpts.JSXFactory, "factory"),
 			Fragment: validateJSX(log, buildOpts.JSXFragment, "fragment"),
@@ -1155,11 +1173,12 @@ func transformImpl(input string, transformOpts TransformOptions) TransformResult
 	}
 
 	// Convert and validate the transformOpts
-	jsFeatures, cssFeatures := validateFeatures(log, transformOpts.Target, transformOpts.Engines)
+	jsFeatures, cssFeatures, targetEnv := validateFeatures(log, transformOpts.Target, transformOpts.Engines)
 	defines, injectedDefines := validateDefines(log, transformOpts.Define, transformOpts.Pure)
 	options := config.Options{
 		UnsupportedJSFeatures:   jsFeatures,
 		UnsupportedCSSFeatures:  cssFeatures,
+		OriginalTargetEnv:       targetEnv,
 		JSX:                     jsx,
 		Defines:                 defines,
 		InjectedDefines:         injectedDefines,

scripts/js-api-tests.js

@@ -3292,6 +3292,16 @@ let transformTests = {
     ])
   },
 
+  async multipleEngineTargetsNotSupported({ esbuild }) {
+    try {
+      await esbuild.transform(`0n`, { target: ['chrome1', 'safari2', 'firefox3'] })
+      throw new Error('Expected an error to be thrown')
+    } catch (e) {
+      assert.strictEqual(e.errors[0].text,
+        'Big integer literals are not available in the configured target environment ("chrome1", "firefox3", "safari2")')
+    }
+  },
+
   // Future syntax
   forAwait: ({ esbuild }) => futureSyntax(esbuild, 'async function foo() { for await (let x of y) {} }', 'es2017', 'es2018'),
   bigInt: ({ esbuild }) => futureSyntax(esbuild, '123n', 'es2019', 'es2020'),