fix #3377: improve resolution error due to null

CHANGELOG.md

@@ -41,6 +41,28 @@
 
     Please never actually write code like this.
 
+* Improve the error message for `null` entries in `exports` ([#3377](https://github.com/evanw/esbuild/issues/3377))
+
+    Package authors can disable package export paths with the `exports` map in `package.json`. With this release, esbuild now has a clearer error message that points to the `null` token in `package.json` itself instead of to the surrounding context. Here is an example of the new error message:
+
+    ```
+    ✘ [ERROR] Could not resolve "msw/browser"
+
+        lib/msw-config.ts:2:28:
+          2 │ import { setupWorker } from 'msw/browser';
+            ╵                             ~~~~~~~~~~~~~
+
+      The path "./browser" cannot be imported from package "msw" because it was explicitly disabled by
+      the package author here:
+
+        node_modules/msw/package.json:17:14:
+          17 │       "node": null,
+             ╵               ~~~~
+
+      You can mark the path "msw/browser" as external to exclude it from the bundle, which will remove
+      this error and leave the unresolved path in the bundle.
+    ```
+
 ## 0.19.2
 
 * Update how CSS nesting is parsed again

internal/bundler_tests/bundler_packagejson_test.go

@@ -2803,3 +2803,41 @@ func TestPackageJsonNodePathsIssue2752(t *testing.T) {
 		},
 	})
 }
+
+// See: https://github.com/evanw/esbuild/issues/3377
+func TestPackageJsonReversePackageExportsIssue3377(t *testing.T) {
+	packagejson_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/lib/msw-config.ts": `
+				import { setupWorker, type SetupWorker } from 'msw/browser'
+				setupWorker();
+			`,
+			"/node_modules/msw/package.json": `{
+				"exports": {
+					"./browser": {
+						"node": null,
+						"require": "./lib/browser/index.js",
+						"import": "./lib/browser/index.mjs",
+						"default": "./lib/browser/index.js"
+					}
+				}
+			}`,
+			"/node_modules/msw/browser/package.json": `{
+				"main": "../lib/browser/index.js",
+				"module": "../lib/browser/index.mjs"
+			}`,
+			"/node_modules/msw/lib/browser/index.js":  `TEST FAILURE`,
+			"/node_modules/msw/lib/browser/index.mjs": `TEST FAILURE`,
+		},
+		entryPaths: []string{"/lib/msw-config.ts"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			AbsOutputFile: "/out.js",
+			Platform:      config.PlatformNode,
+		},
+		expectedScanLog: `lib/msw-config.ts: ERROR: Could not resolve "msw/browser"
+node_modules/msw/package.json: NOTE: The path "./browser" cannot be imported from package "msw" because it was explicitly disabled by the package author here:
+NOTE: You can mark the path "msw/browser" as external to exclude it from the bundle, which will remove this error and leave the unresolved path in the bundle.
+`,
+	})
+}

internal/resolver/package_json.go

@@ -808,6 +808,9 @@ type pjDebug struct {
 
 	// This is the range of the token to use for error messages
 	token logger.Range
+
+	// If true, the token is a "null" literal
+	isBecauseOfNullLiteral bool
 }
 
 func (r resolverQuery) esmHandlePostConditions(
@@ -892,6 +895,7 @@ func (r resolverQuery) esmPackageExportsResolve(
 		return "", pjStatusInvalidPackageConfiguration, pjDebug{token: exports.firstToken}
 	}
 
+	debugToReturn := pjDebug{token: exports.firstToken}
 	if subpath == "." {
 		mainExport := pjEntry{kind: pjNull}
 		if exports.kind == pjString || exports.kind == pjArray || (exports.kind == pjObject && !exports.keysStartWithDot()) {
@@ -908,19 +912,23 @@ func (r resolverQuery) esmPackageExportsResolve(
 			resolved, status, debug := r.esmPackageTargetResolve(packageURL, mainExport, "", false, false, conditions)
 			if status != pjStatusNull && status != pjStatusUndefined {
 				return resolved, status, debug
+			} else {
+				debugToReturn = debug
 			}
 		}
 	} else if exports.kind == pjObject && exports.keysStartWithDot() {
 		resolved, status, debug := r.esmPackageImportsExportsResolve(subpath, exports, packageURL, false, conditions)
 		if status != pjStatusNull && status != pjStatusUndefined {
 			return resolved, status, debug
+		} else {
+			debugToReturn = debug
 		}
 	}
 
 	if r.debugLogs != nil {
 		r.debugLogs.addNote(fmt.Sprintf("The path %q is not exported", subpath))
 	}
-	return "", pjStatusPackagePathNotExported, pjDebug{token: exports.firstToken}
+	return "", pjStatusPackagePathNotExported, debugToReturn
 }
 
 func (r resolverQuery) esmPackageImportsExportsResolve(
@@ -1237,7 +1245,7 @@ func (r resolverQuery) esmPackageTargetResolve(
 		if r.debugLogs != nil {
 			r.debugLogs.addNote(fmt.Sprintf("The path %q is set to null", subpath))
 		}
-		return "", pjStatusNull, pjDebug{token: target.firstToken}
+		return "", pjStatusNull, pjDebug{token: target.firstToken, isBecauseOfNullLiteral: true}
 	}
 
 	if r.debugLogs != nil {

internal/resolver/resolver.go

@@ -2609,6 +2609,12 @@ func (r resolverQuery) finalizeImportsExportsResult(
 		r.debugMeta.notes = []logger.MsgData{tracker.MsgData(debug.token, why)}
 
 	case pjStatusPackagePathNotExported:
+		if debug.isBecauseOfNullLiteral {
+			r.debugMeta.notes = []logger.MsgData{tracker.MsgData(debug.token,
+				fmt.Sprintf("The path %q cannot be imported from package %q because it was explicitly disabled by the package author here:", esmPackageSubpath, esmPackageName))}
+			break
+		}
+
 		r.debugMeta.notes = []logger.MsgData{tracker.MsgData(debug.token,
 			fmt.Sprintf("The path %q is not exported by package %q:", esmPackageSubpath, esmPackageName))}
 
@@ -2706,7 +2712,10 @@ func (r resolverQuery) finalizeImportsExportsResult(
 				}
 
 			default:
-				if !didSuggestEnablingCondition {
+				// Note: Don't suggest the adding the "types" condition because
+				// TypeScript uses that for type definitions, which are not
+				// intended to be included in a bundle as executable code
+				if !didSuggestEnablingCondition && key.Text != "types" {
 					var how string
 					switch logger.API {
 					case logger.CLIAPI: