Improve flow coverage in Metro

Reviewed By: mjesun

Differential Revision: D14258819

fbshipit-source-id: 72cd19789d1c651238334a016581217ad7278999

packages/metro/src/Bundler/util.js

@@ -146,7 +146,7 @@ function isAssetTypeAnImage(type: string): boolean {
   );
 }
 
-function filterObject(object, blacklist) {
+function filterObject(object: AssetDataWithoutFiles, blacklist: Set<string>) {
   const copied = Object.assign({}, object);
   for (const key of blacklist) {
     delete copied[key];
@@ -209,7 +209,10 @@ function createRamBundleGroups<T: ModuleTransportLike>(
   return result;
 }
 
-function* filter(iterator, predicate) {
+function* filter(
+  iterator: ArrayMap<number, number>,
+  predicate: ([number, Array<number>]) => boolean,
+) {
   for (const value of iterator) {
     if (predicate(value)) {
       yield value;

packages/metro/src/DeltaBundler/Transformer.js

@@ -143,7 +143,7 @@ class Transformer {
   }
 }
 
-function verifyRootExists(root) {
+function verifyRootExists(root: string) {
   // Verify that the root exists.
   assert(fs.statSync(root).isDirectory(), 'Root has to be a valid directory');
 }

packages/metro/src/DeltaBundler/WorkerFarm.js

@@ -143,7 +143,7 @@ class WorkerFarm {
     return null;
   }
 
-  _formatGenericError(err, filename) {
+  _formatGenericError(err, filename: string) {
     const error = new TransformError(`${filename}: ${err.message}`);
 
     return Object.assign(error, {
@@ -155,7 +155,7 @@ class WorkerFarm {
     });
   }
 
-  _formatBabelError(err, filename) {
+  _formatBabelError(err, filename: string) {
     const error = new TransformError(
       `${err.type || 'Error'}${
         err.message.includes(filename) ? '' : ' in ' + filename

packages/metro/src/lib/getPreludeCode.js

@@ -30,7 +30,7 @@ function getPreludeCode({
 
 const excluded = new Set(['__BUNDLE_START_TIME__', '__DEV__', 'process']);
 
-function formatExtraVars(extraVars) {
+function formatExtraVars(extraVars: ?{[string]: mixed}) {
   const assignments = [];
 
   for (const key in extraVars) {
@@ -42,7 +42,7 @@ function formatExtraVars(extraVars) {
   return assignments;
 }
 
-function processEnv(nodeEnv) {
+function processEnv(nodeEnv: string) {
   return `process.env=process.env||{};process.env.NODE_ENV=process.env.NODE_ENV||${JSON.stringify(
     nodeEnv,
   )};`;

packages/metro/src/node-haste/DependencyGraph/ResolutionRequest.js

@@ -111,7 +111,7 @@ class ResolutionRequest<TModule: Moduleish, TPackage: Packageish> {
   }
 }
 
-function getResolutionCacheKey(modulePath, depName) {
+function getResolutionCacheKey(modulePath: string, depName: string) {
   return `${path.resolve(modulePath)}:${depName}`;
 }
 

packages/metro/src/shared/output/RamBundle/as-indexed-file.js

@@ -97,24 +97,35 @@ function writeBuffers(stream, buffers: Array<Buffer>) {
   });
 }
 
-function nullTerminatedBuffer(contents, encoding) {
+function nullTerminatedBuffer(
+  contents: string,
+  encoding: void | 'ascii' | 'utf16le' | 'utf8',
+) {
   return Buffer.concat([Buffer.from(contents, encoding), nullByteBuffer]);
 }
 
-function moduleToBuffer(id, code, encoding) {
+function moduleToBuffer(
+  id: number,
+  code: string,
+  encoding: void | 'ascii' | 'utf16le' | 'utf8',
+) {
   return {
     id,
     buffer: nullTerminatedBuffer(code, encoding),
   };
 }
 
-function entryOffset(n) {
+function entryOffset(n: number) {
   // 2: num_entries + startup_code_len
   // n * 2: each entry consists of two uint32s
   return (2 + n * 2) * SIZEOF_UINT32;
 }
 
-function buildModuleTable(startupCode, moduleBuffers, moduleGroups) {
+function buildModuleTable(
+  startupCode: Buffer,
+  moduleBuffers: Array<{buffer: Buffer, id: number}>,
+  moduleGroups: ModuleGroups,
+) {
   // table format:
   // - num_entries:      uint_32  number of entries
   // - startup_code_len: uint_32  length of the startup section
@@ -124,7 +135,7 @@ function buildModuleTable(startupCode, moduleBuffers, moduleGroups) {
   //  - module_offset:   uint_32  offset into the modules blob
   //  - module_length:   uint_32  length of the module code in bytes
 
-  const moduleIds = Array.from(moduleGroups.modulesById.keys());
+  const moduleIds = [...moduleGroups.modulesById.keys()];
   const maxId = moduleIds.reduce((max, id) => Math.max(max, id));
   const numEntries = maxId + 1;
   const table: Buffer = Buffer.alloc(entryOffset(numEntries)).fill(0);
@@ -154,7 +165,11 @@ function buildModuleTable(startupCode, moduleBuffers, moduleGroups) {
   return table;
 }
 
-function groupCode(rootCode, moduleGroup, modulesById) {
+function groupCode(
+  rootCode: string,
+  moduleGroup: void | Set<number>,
+  modulesById: Map<number, ModuleTransportLike>,
+) {
   if (!moduleGroup || !moduleGroup.size) {
     return rootCode;
   }
@@ -166,7 +181,11 @@ function groupCode(rootCode, moduleGroup, modulesById) {
   return code.join('\n');
 }
 
-function buildModuleBuffers(modules, moduleGroups, encoding) {
+function buildModuleBuffers(
+  modules: $ReadOnlyArray<ModuleTransportLike>,
+  moduleGroups: ModuleGroups,
+  encoding: void | 'ascii' | 'utf16le' | 'utf8',
+): Array<{buffer: Buffer, id: number}> {
   return modules
     .filter(m => !moduleGroups.modulesInGroups.has(m.id))
     .map(({id, code}) =>
@@ -214,7 +233,7 @@ function createModuleGroups(
   };
 }
 
-function* concat(iterators) {
+function* concat(iterators: Iterator<Set<number>>) {
   for (const it of iterators) {
     yield* it;
   }

packages/metro/src/shared/output/RamBundle/util.js

@@ -76,8 +76,8 @@ function combineSourceMapsAddingOffsets(
 function combineMaps(
   modules: $ReadOnlyArray<ModuleTransportLike>,
   offsets: ?Array<number>,
-  moduleGroups,
-  options,
+  moduleGroups: ?ModuleGroups,
+  options: ?CombineOptions,
 ) {
   const sections = [];
 

packages/metro/src/shared/output/meta.js

@@ -41,7 +41,10 @@ module.exports = function(
   return signature;
 };
 
-function tryAsciiPromotion(buffer, encoding) {
+function tryAsciiPromotion(
+  buffer: Buffer,
+  encoding: 'ascii' | 'utf16le' | 'utf8',
+) {
   if (!isUTF8(encoding)) {
     return encoding;
   }
@@ -53,7 +56,10 @@ function tryAsciiPromotion(buffer, encoding) {
   return 'ascii';
 }
 
-function asBuffer(x, encoding): Buffer {
+function asBuffer(
+  x: Buffer | string,
+  encoding: 'ascii' | 'utf16le' | 'utf8',
+): Buffer {
   if (typeof x !== 'string') {
     return x;
   }