fix #423: ignore invalid "main" in "package.json"

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+* Recover from bad `main` field in `package.json` ([#423](https://github.com/evanw/esbuild/issues/423))
+
+    Some packages are published with invalid information in the `main` field of `package.json`. In that case, path resolution should fall back to searching for a file named `index.js` before giving up. This matters for the `simple-exiftool` package, for example.
+
 ## 0.7.9
 
 * Fixed panic when using a `url()` import in CSS with the `--metafile` option

internal/bundler/bundler_packagejson_test.go

@@ -36,6 +36,32 @@ func TestPackageJsonMain(t *testing.T) {
 	})
 }
 
+func TestPackageJsonBadMain(t *testing.T) {
+	packagejson_suite.expectBundled(t, bundled{
+		files: map[string]string{
+			"/Users/user/project/src/entry.js": `
+				import fn from 'demo-pkg'
+				console.log(fn())
+			`,
+			"/Users/user/project/node_modules/demo-pkg/package.json": `
+				{
+					"main": "./does-not-exist.js"
+				}
+			`,
+			"/Users/user/project/node_modules/demo-pkg/index.js": `
+				module.exports = function() {
+					return 123
+				}
+			`,
+		},
+		entryPaths: []string{"/Users/user/project/src/entry.js"},
+		options: config.Options{
+			Mode:          config.ModeBundle,
+			AbsOutputFile: "/Users/user/project/out.js",
+		},
+	})
+}
+
 func TestPackageJsonSyntaxErrorComment(t *testing.T) {
 	packagejson_suite.expectBundled(t, bundled{
 		files: map[string]string{

internal/bundler/snapshots/snapshots_packagejson.txt

@@ -1,3 +1,17 @@
+TestPackageJsonBadMain
+---------- /Users/user/project/out.js ----------
+// /Users/user/project/node_modules/demo-pkg/index.js
+var require_demo_pkg = __commonJS((exports, module) => {
+  module.exports = function() {
+    return 123;
+  };
+});
+
+// /Users/user/project/src/entry.js
+const demo_pkg = __toModule(require_demo_pkg());
+console.log(demo_pkg.default());
+
+================================================================================
 TestPackageJsonBrowserMapAvoidMissing
 ---------- /Users/user/project/out.js ----------
 // /Users/user/project/node_modules/component-indexof/index.js

internal/resolver/resolver.go

@@ -790,12 +790,9 @@ func (r *resolver) dirInfoUncached(path string) *dirInfo {
 		info.tsConfigJson = parentInfo.tsConfigJson
 	}
 
-	// Are all main fields from "package.json" missing?
-	if info.packageJson == nil || info.packageJson.absMainFields == nil {
-		// Look for an "index" file with known extensions
-		if absolute, ok := r.loadAsIndex(path, entries); ok {
-			info.absPathIndex = &absolute
-		}
+	// Look for an "index" file with known extensions
+	if absolute, ok := r.loadAsIndex(path, entries); ok {
+		info.absPathIndex = &absolute
 	}
 
 	return info