fix #3834: cli sometimes panics with --analyze

CHANGELOG.md

@@ -20,6 +20,10 @@
     fs.open;
     ```
 
+* Fix a panic when using the CLI with invalid build flags if `--analyze` is present ([#3834](https://github.com/evanw/esbuild/issues/3834))
+
+    Previously esbuild's CLI could crash if it was invoked with flags that aren't valid for a "build" API call and the `--analyze` flag is present. This was caused by esbuild's internals attempting to add a Go plugin (which is how `--analyze` is implemented) to a null build object. The panic has been fixed in this release.
+
 ## 0.23.0
 
 **_This release deliberately contains backwards-incompatible changes._** To avoid automatically picking up releases like this, you should either be pinning the exact version of `esbuild` in your `package.json` file (recommended) or be using a version range syntax that only accepts patch upgrades such as `^0.22.0` or `~0.22.0`. See npm's documentation about [semver](https://docs.npmjs.com/cli/v6/using-npm/semver/) for more information.

pkg/cli/cli_impl.go

@@ -1023,11 +1023,15 @@ outer:
 	return
 }
 
+func isArgForBuild(arg string) bool {
+	return !strings.HasPrefix(arg, "-") || arg == "--bundle"
+}
+
 // This returns either BuildOptions, TransformOptions, or an error
 func parseOptionsForRun(osArgs []string) (*api.BuildOptions, *api.TransformOptions, parseOptionsExtras, *cli_helpers.ErrorWithNote) {
 	// If there's an entry point or we're bundling, then we're building
 	for _, arg := range osArgs {
-		if !strings.HasPrefix(arg, "-") || arg == "--bundle" {
+		if isArgForBuild(arg) {
 			options := newBuildOptions()
 
 			// Apply defaults appropriate for the CLI
@@ -1091,20 +1095,25 @@ const (
 )
 
 func filterAnalyzeFlags(osArgs []string) ([]string, analyzeMode) {
-	analyze := analyzeDisabled
-	end := 0
 	for _, arg := range osArgs {
-		switch arg {
-		case "--analyze":
-			analyze = analyzeEnabled
-		case "--analyze=verbose":
-			analyze = analyzeVerbose
-		default:
-			osArgs[end] = arg
-			end++
+		if isArgForBuild(arg) {
+			analyze := analyzeDisabled
+			end := 0
+			for _, arg := range osArgs {
+				switch arg {
+				case "--analyze":
+					analyze = analyzeEnabled
+				case "--analyze=verbose":
+					analyze = analyzeVerbose
+				default:
+					osArgs[end] = arg
+					end++
+				}
+			}
+			return osArgs[:end], analyze
 		}
 	}
-	return osArgs[:end], analyze
+	return osArgs, analyzeDisabled
 }
 
 // Print metafile analysis after the build if it's enabled
@@ -1150,10 +1159,11 @@ func runImpl(osArgs []string, plugins []api.Plugin) int {
 	// Add any plugins from the caller after parsing the build options
 	if buildOptions != nil {
 		buildOptions.Plugins = append(buildOptions.Plugins, plugins...)
-	}
 
-	if analyze != analyzeDisabled {
-		addAnalyzePlugin(buildOptions, analyze, osArgs)
+		// The "--analyze" flag is implemented as a plugin
+		if analyze != analyzeDisabled {
+			addAnalyzePlugin(buildOptions, analyze, osArgs)
+		}
 	}
 
 	switch {

scripts/end-to-end-tests.js

@@ -8446,6 +8446,27 @@ tests.push(
   }),
 )
 
+// Tests for analyze
+tests.push(
+  test(['in.js', '--analyze', '--outfile=node.js'], {
+    'in.js': `let x = 1 + 2`,
+  }, {
+    expectedStderr: `
+  node.js   15b   100.0%
+   └ in.js  15b   100.0%
+
+`,
+  }),
+  test(['in.js', '--invalid-flag', '--analyze'], {
+    'in.js': `let x = 1 + 2`,
+  }, {
+    expectedStderr: `${errorIcon} [ERROR] Invalid build flag: "--invalid-flag"\n\n`,
+  }),
+  test(['--analyze'], {}, {
+    expectedStderr: `${errorIcon} [ERROR] Invalid transform flag: "--analyze"\n\n`,
+  }),
+)
+
 // Test writing to stdout
 tests.push(
   // These should succeed