Add a plugin to warn if the source type is ambiguous

lib/WarnAmbiguousSourceTypePlugin.js

@@ -0,0 +1,74 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Florent Cailhol @ooflorent
+*/
+"use strict";
+
+const WebpackError = require("./WebpackError");
+
+class WarnAmbiguousSourceTypePlugin {
+	apply(compiler) {
+		compiler.hooks.compilation.tap(
+			"WarnAmbiguousSourceTypePlugin",
+			(compilation, { normalModuleFactory }) => {
+				normalModuleFactory.hooks.parser
+					.for("javascript/auto")
+					.tap("WarnAmbiguousSourceTypePlugin", parser => {
+						function flagAsDynamic() {
+							const module = parser.state.module;
+							if (!module.buildInfo) module.buildInfo = {};
+							module.buildInfo.dynamic = true;
+						}
+						parser.hooks.call
+							.for("define")
+							.tap("WarnAmbiguousSourceTypePlugin", flagAsDynamic);
+						parser.hooks.call
+							.for("require")
+							.tap("WarnAmbiguousSourceTypePlugin", flagAsDynamic);
+						parser.hooks.call
+							.for("require.resolve")
+							.tap("WarnAmbiguousSourceTypePlugin", flagAsDynamic);
+						parser.hooks.expression
+							.for("module")
+							.tap("WarnAmbiguousSourceTypePlugin", flagAsDynamic);
+						parser.hooks.expression
+							.for("exports")
+							.tap("WarnAmbiguousSourceTypePlugin", flagAsDynamic);
+					});
+				compilation.hooks.finishModules.tap(
+					"WarnAmbiguousSourceTypePlugin",
+					modules => {
+						for (const module of modules) {
+							if (module.type === "javascript/auto") {
+								if (
+									module.buildMeta &&
+									module.buildMeta.exportsType &&
+									module.buildInfo &&
+									module.buildInfo.dynamic
+								) {
+									compilation.warnings.push(
+										new AmbiguousSourceTypeWarning(module)
+									);
+								}
+							}
+						}
+					}
+				);
+			}
+		);
+	}
+}
+
+class AmbiguousSourceTypeWarning extends WebpackError {
+	constructor(module) {
+		super();
+
+		this.name = "AmbiguousSourceTypeWarning";
+		this.message = "Source type is ambiguous";
+		this.origin = this.module = module;
+
+		Error.captureStackTrace(this, this.constructor);
+	}
+}
+
+module.exports = WarnAmbiguousSourceTypePlugin;

lib/webpack.js

@@ -117,6 +117,8 @@ exportPlugins(exports, {
 	SourceMapDevToolPlugin: () => require("./SourceMapDevToolPlugin"),
 	Stats: () => require("./Stats"),
 	UmdMainTemplatePlugin: () => require("./UmdMainTemplatePlugin"),
+	WarnAmbiguousSourceTypePlugin: () =>
+		require("./WarnAmbiguousSourceTypePlugin"),
 	WatchIgnorePlugin: () => require("./WatchIgnorePlugin")
 });
 exportPlugins((exports.optimize = {}), {

test/configCases/parsing/ambiguous/cases/amb1.js

@@ -0,0 +1,2 @@
+import "./empty";
+exports.type = "ambiguous";

test/configCases/parsing/ambiguous/cases/amb2.js

@@ -0,0 +1,2 @@
+require("./empty");
+export default "ambiguous";

test/configCases/parsing/ambiguous/cases/amb3.js

@@ -0,0 +1,2 @@
+require.resolve("./empty");
+export default "ambiguous";

test/configCases/parsing/ambiguous/cases/amb4.js

@@ -0,0 +1,2 @@
+import "./empty";
+require("./empty");

test/configCases/parsing/ambiguous/cases/amb5.js

@@ -0,0 +1,5 @@
+import "./empty";
+
+Object.assign({}, module.exports, {
+	type: "ambiguous"
+});

test/configCases/parsing/ambiguous/cases/amb6.js

@@ -0,0 +1,5 @@
+import "./empty";
+
+Object.assign({}, exports, {
+	type: "ambiguous"
+});

test/configCases/parsing/ambiguous/cases/dyn.js

@@ -0,0 +1,5 @@
+require("./empty");
+require.resolve("./empty");
+
+module.exports = {};
+exports.x = true;

test/configCases/parsing/ambiguous/cases/esm.js

@@ -0,0 +1,7 @@
+import "./empty";
+
+let define = () => {};
+let require = () => {};
+
+define();
+require();

test/configCases/parsing/ambiguous/index.js

@@ -0,0 +1,10 @@
+it("should compile and run the test", () => {
+	require("./cases/amb1");
+	require("./cases/amb2");
+	require("./cases/amb3");
+	require("./cases/amb4");
+	require("./cases/amb5");
+	require("./cases/amb6");
+	require("./cases/dyn");
+	require("./cases/esm");
+});

test/configCases/parsing/ambiguous/warnings.js

@@ -0,0 +1,5 @@
+module.exports = [];
+
+for (let i = 1; i <= 6; ++i) {
+	module.exports.push([new RegExp(`amb${i}`), /ambiguous/]);
+}

test/configCases/parsing/ambiguous/webpack.config.js

@@ -0,0 +1,5 @@
+const webpack = require("../../../../");
+
+module.exports = {
+	plugins: [new webpack.WarnAmbiguousSourceTypePlugin()]
+};