fix #3887: omit dead export warning for default

Author: evanw

internal/bundler_tests/bundler_packagejson_test.go

@@ -3002,3 +3002,36 @@ node_modules/foo/package.json: NOTE: The "default" condition comes earlier and w
 `,
 	})
 }
+
+// See: https://github.com/evanw/esbuild/issues/3887
+func TestPackageJsonExportsDefaultWarningIssue3887(t *testing.T) {
+	packagejson_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/entry.js": `
+				import "foo"
+			`,
+			"/node_modules/foo/dist/index.js": `
+				success()
+			`,
+			"/node_modules/foo/package.json": `
+				{
+					"exports": {
+						".": {
+							"node": "./dist/index.js",
+							"require": "./dist/index.js",
+							"import": "./dist/index.esm.js",
+							"default": "./dist/index.esm.js"
+						}
+					}
+				}
+			`,
+		},
+		entryPaths: []string{"/entry.js"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			Platform:      config.PlatformNode,
+			AbsOutputFile: "/out.js",
+		},
+		debugLogs: true,
+	})
+}

internal/bundler_tests/snapshots/snapshots_packagejson.txt

@@ -585,6 +585,12 @@ TestPackageJsonExportsDefaultOverImportAndRequire
 // Users/user/project/node_modules/pkg/default.js
 console.log("SUCCESS");
 
+================================================================================
+TestPackageJsonExportsDefaultWarningIssue3887
+---------- /out.js ----------
+// node_modules/foo/dist/index.js
+success();
+
 ================================================================================
 TestPackageJsonExportsEntryPointImportOverRequire
 ---------- /out.js ----------

internal/resolver/package_json.go

@@ -710,7 +710,8 @@ func parseImportsExportsMap(source logger.Source, log logger.Log, json js_ast.Ex
 				// Track "dead" conditional branches that can never be reached
 				if foundDefault.Len != 0 || (foundImport.Len != 0 && foundRequire.Len != 0) {
 					deadCondition.ranges = append(deadCondition.ranges, keyRange)
-					if deadCondition.reason == "" {
+					// Note: Don't warn about the "default" condition as it's supposed to be a catch-all condition
+					if deadCondition.reason == "" && key != "default" {
 						if foundDefault.Len != 0 {
 							deadCondition.reason = "\"default\""
 							deadCondition.notes = []logger.MsgData{