Add configuration option to suppress require cycle warnings

docs/Configuration.md

@@ -211,6 +211,14 @@ Type: `Array<string>`
 
 Additional platforms to look out for, For example, if you want to add a "custom" platform, and use modules ending in .custom.js, you would return ['custom'] here.
 
+#### `requireCycleIgnorePatterns`
+
+Type: `Array<RegExp>` (default: `[/(^|\/|\\)node_modules($|\/|\\)/]`)
+
+In development mode, suppress require cycle warnings for any cycle involving a module that matches any of these expressions. This is useful for third-party code and first-party expected cycles.
+
+Note that if you specify your own value for this config option it will replace (not concatenate with) Metro's default.
+
 ---
 ### Transformer Options
 

packages/metro-config/src/__tests__/__snapshots__/loadConfig-test.js.snap

@@ -58,6 +58,9 @@ Object {
       "windows",
       "web",
     ],
+    "requireCycleIgnorePatterns": Array [
+      /\\(\\^\\|\\\\/\\|\\\\\\\\\\)node_modules\\(\\$\\|\\\\/\\|\\\\\\\\\\)/,
+    ],
     "resolveRequest": null,
     "resolverMainFields": Array [
       "browser",
@@ -204,6 +207,9 @@ Object {
       "windows",
       "web",
     ],
+    "requireCycleIgnorePatterns": Array [
+      /\\(\\^\\|\\\\/\\|\\\\\\\\\\)node_modules\\(\\$\\|\\\\/\\|\\\\\\\\\\)/,
+    ],
     "resolveRequest": null,
     "resolverMainFields": Array [
       "browser",
@@ -350,6 +356,9 @@ Object {
       "windows",
       "web",
     ],
+    "requireCycleIgnorePatterns": Array [
+      /\\(\\^\\|\\\\/\\|\\\\\\\\\\)node_modules\\(\\$\\|\\\\/\\|\\\\\\\\\\)/,
+    ],
     "resolveRequest": null,
     "resolverMainFields": Array [
       "browser",
@@ -496,6 +505,9 @@ Object {
       "windows",
       "web",
     ],
+    "requireCycleIgnorePatterns": Array [
+      /\\(\\^\\|\\\\/\\|\\\\\\\\\\)node_modules\\(\\$\\|\\\\/\\|\\\\\\\\\\)/,
+    ],
     "resolveRequest": null,
     "resolverMainFields": Array [
       "browser",

packages/metro-config/src/configTypes.flow.js

@@ -85,6 +85,7 @@ type ResolverConfigT = {
   resolverMainFields: $ReadOnlyArray<string>,
   sourceExts: $ReadOnlyArray<string>,
   useWatchman: boolean,
+  requireCycleIgnorePatterns: $ReadOnlyArray<RegExp>,
 };
 
 type SerializerConfigT = {

packages/metro-config/src/defaults/index.js

@@ -47,6 +47,7 @@ const getDefaultValues = (projectRoot: ?string): ConfigT => ({
     resolveRequest: null,
     resolverMainFields: ['browser', 'main'],
     useWatchman: true,
+    requireCycleIgnorePatterns: [/(^|\/|\\)node_modules($|\/|\\)/],
   },
 
   serializer: {

packages/metro-runtime/src/polyfills/__tests__/require-test.js

@@ -19,8 +19,14 @@ function createModule(
   verboseName,
   factory,
   dependencyMap = [],
+  globalPrefix = '',
 ) {
-  moduleSystem.__d(factory, moduleId, dependencyMap, verboseName);
+  moduleSystem[globalPrefix + '__d'](
+    factory,
+    moduleId,
+    dependencyMap,
+    verboseName,
+  );
 }
 
 describe('require', () => {
@@ -665,6 +671,51 @@ describe('require', () => {
       console.warn = warn;
     });
 
+    it('does not log warning for cyclic dependency in ignore list', () => {
+      moduleSystem.__customPrefix__requireCycleIgnorePatterns = [/foo/];
+      createModuleSystem(moduleSystem, true, '__customPrefix');
+
+      createModule(
+        moduleSystem,
+        0,
+        'foo.js',
+        (global, require) => {
+          require(1);
+        },
+        [],
+        '__customPrefix',
+      );
+
+      createModule(
+        moduleSystem,
+        1,
+        'bar.js',
+        (global, require) => {
+          require(2);
+        },
+        [],
+        '__customPrefix',
+      );
+
+      createModule(
+        moduleSystem,
+        2,
+        'baz.js',
+        (global, require) => {
+          require(0);
+        },
+        [],
+        '__customPrefix',
+      );
+
+      const warn = console.warn;
+      console.warn = jest.fn();
+
+      moduleSystem.__r(0);
+      expect(console.warn).toHaveBeenCalledTimes(0);
+      console.warn = warn;
+    });
+
     it('sets the exports value to their current value', () => {
       createModuleSystem(moduleSystem, false, '');
 

packages/metro-runtime/src/polyfills/require.js

@@ -177,13 +177,15 @@ function metroRequire(moduleId: ModuleID | VerboseModuleNameForDev): Exports {
         .map((id: number) =>
           modules[id] ? modules[id].verboseName : '[unknown]',
         );
-      // We want to show A -> B -> A:
-      cycle.push(cycle[0]);
-      console.warn(
-        `Require cycle: ${cycle.join(' -> ')}\n\n` +
-          'Require cycles are allowed, but can result in uninitialized values. ' +
-          'Consider refactoring to remove the need for a cycle.',
-      );
+
+      if (shouldPrintRequireCycle(cycle)) {
+        cycle.push(cycle[0]); // We want to print A -> B -> A:
+        console.warn(
+          `Require cycle: ${cycle.join(' -> ')}\n\n` +
+            'Require cycles are allowed, but can result in uninitialized values. ' +
+            'Consider refactoring to remove the need for a cycle.',
+        );
+      }
     }
   }
 
@@ -194,6 +196,22 @@ function metroRequire(moduleId: ModuleID | VerboseModuleNameForDev): Exports {
     : guardedLoadModule(moduleIdReallyIsNumber, module);
 }
 
+// We print require cycles unless they match a pattern in the
+// `requireCycleIgnorePatterns` configuration.
+function shouldPrintRequireCycle(modules: $ReadOnlyArray<?string>): boolean {
+  const regExps =
+    global[__METRO_GLOBAL_PREFIX__ + '__requireCycleIgnorePatterns'];
+  if (!regExps || !Array.isArray(regExps)) {
+    return true;
+  }
+
+  const isIgnored = module =>
+    module != null && regExps.some(regExp => regExp.test(module));
+
+  // Print the cycle unless any part of it is ignored
+  return modules.every(module => !isIgnored(module));
+}
+
 function metroImportDefault(moduleId: ModuleID | VerboseModuleNameForDev) {
   if (__DEV__ && typeof moduleId === 'string') {
     const verboseName = moduleId;

packages/metro/src/lib/__tests__/getPreludeCode-test.js

@@ -17,12 +17,16 @@ const vm = require('vm');
 ['development', 'production'].forEach((mode: string) => {
   describe(`${mode} mode`, () => {
     const isDev = mode === 'development';
-    const globalPrefix = '';
+    const globalPrefix = '__metro';
+    const requireCycleIgnorePatterns = [];
 
     it('sets up `process.env.NODE_ENV` and `__DEV__`', () => {
       const sandbox: $FlowFixMe = {};
       vm.createContext(sandbox);
-      vm.runInContext(getPreludeCode({isDev, globalPrefix}), sandbox);
+      vm.runInContext(
+        getPreludeCode({isDev, globalPrefix, requireCycleIgnorePatterns}),
+        sandbox,
+      );
       expect(sandbox.process.env.NODE_ENV).toEqual(mode);
       expect(sandbox.__DEV__).toEqual(isDev);
     });
@@ -31,17 +35,51 @@ const vm = require('vm');
       const sandbox: $FlowFixMe = {};
       vm.createContext(sandbox);
       vm.runInContext(
-        getPreludeCode({isDev, globalPrefix: '__metro'}),
+        getPreludeCode({
+          isDev,
+          globalPrefix: '__customPrefix',
+          requireCycleIgnorePatterns,
+        }),
+        sandbox,
+      );
+      expect(sandbox.__METRO_GLOBAL_PREFIX__).toBe('__customPrefix');
+    });
+
+    it('sets up `${globalPrefix}__requireCycleIgnorePatterns` in development', () => {
+      const sandbox: $FlowFixMe = {};
+      vm.createContext(sandbox);
+      vm.runInContext(
+        getPreludeCode({
+          isDev,
+          globalPrefix,
+          requireCycleIgnorePatterns: [
+            /blah/,
+            /(^|\/|\\)node_modules($|\/|\\)/,
+          ],
+        }),
         sandbox,
       );
-      expect(sandbox.__METRO_GLOBAL_PREFIX__).toBe('__metro');
+
+      if (isDev) {
+        expect(sandbox[`${globalPrefix}__requireCycleIgnorePatterns`]).toEqual([
+          /blah/,
+          /(^|\/|\\)node_modules($|\/|\\)/,
+        ]);
+      } else {
+        expect(
+          sandbox[`${globalPrefix}__requireCycleIgnorePatterns`],
+        ).not.toBeDefined();
+      }
     });
 
     it('does not override an existing `process.env`', () => {
       const nextTick = () => {};
       const sandbox: $FlowFixMe = {process: {nextTick, env: {FOOBAR: 123}}};
       vm.createContext(sandbox);
-      vm.runInContext(getPreludeCode({isDev, globalPrefix}), sandbox);
+      vm.runInContext(
+        getPreludeCode({isDev, globalPrefix, requireCycleIgnorePatterns}),
+        sandbox,
+      );
       expect(sandbox.process.env.NODE_ENV).toEqual(mode);
       expect(sandbox.process.env.FOOBAR).toEqual(123);
       expect(sandbox.process.nextTick).toEqual(nextTick);
@@ -53,7 +91,12 @@ const vm = require('vm');
       const BAR = 2;
       vm.createContext(sandbox);
       vm.runInContext(
-        getPreludeCode({isDev, globalPrefix, extraVars: {FOO, BAR}}),
+        getPreludeCode({
+          isDev,
+          globalPrefix,
+          requireCycleIgnorePatterns,
+          extraVars: {FOO, BAR},
+        }),
         sandbox,
       );
       expect(sandbox.FOO).toBe(FOO);
@@ -64,7 +107,12 @@ const vm = require('vm');
       const sandbox: $FlowFixMe = {};
       vm.createContext(sandbox);
       vm.runInContext(
-        getPreludeCode({isDev, globalPrefix, extraVars: {__DEV__: 123}}),
+        getPreludeCode({
+          isDev,
+          globalPrefix,
+          requireCycleIgnorePatterns,
+          extraVars: {__DEV__: 123},
+        }),
         sandbox,
       );
       expect(sandbox.__DEV__).toBe(isDev);

packages/metro/src/lib/getPreludeCode.js

@@ -14,18 +14,33 @@ function getPreludeCode({
   extraVars,
   isDev,
   globalPrefix,
+  requireCycleIgnorePatterns,
 }: {
   +extraVars?: {[string]: mixed, ...},
   +isDev: boolean,
   +globalPrefix: string,
+  +requireCycleIgnorePatterns: $ReadOnlyArray<RegExp>,
 }): string {
   const vars = [
+    // Ensure these variable names match the ones referenced in metro-runtime
+    // require.js
     '__BUNDLE_START_TIME__=this.nativePerformanceNow?nativePerformanceNow():Date.now()',
     `__DEV__=${String(isDev)}`,
     ...formatExtraVars(extraVars),
     'process=this.process||{}',
     `__METRO_GLOBAL_PREFIX__='${globalPrefix}'`,
   ];
+
+  if (isDev) {
+    // Ensure these variable names match the ones referenced in metro-runtime
+    // require.js
+    vars.push(
+      `${globalPrefix}__requireCycleIgnorePatterns=[${requireCycleIgnorePatterns
+        .map(regex => regex.toString())
+        .join(',')}]`,
+    );
+  }
+
   return `var ${vars.join(',')};${processEnv(
     isDev ? 'development' : 'production',
   )}`;

packages/metro/src/lib/getPrependedScripts.js

@@ -69,6 +69,7 @@ async function getPrependedScripts(
     _getPrelude({
       dev: options.dev,
       globalPrefix: config.transformer.globalPrefix,
+      requireCycleIgnorePatterns: config.resolver.requireCycleIgnorePatterns,
     }),
     ...dependencies.values(),
   ];
@@ -77,12 +78,18 @@ async function getPrependedScripts(
 function _getPrelude({
   dev,
   globalPrefix,
+  requireCycleIgnorePatterns,
 }: {
   dev: boolean,
   globalPrefix: string,
+  requireCycleIgnorePatterns: $ReadOnlyArray<RegExp>,
   ...
 }): Module<> {
-  const code = getPreludeCode({isDev: dev, globalPrefix});
+  const code = getPreludeCode({
+    isDev: dev,
+    globalPrefix,
+    requireCycleIgnorePatterns,
+  });
   const name = '__prelude__';
 
   return {