Add core cache of pre-resolved paths

This reduces the number of calls to Module._findPath for
relative paths since they can be resolved without stating

build/tasks/generate-module-cache-task.coffee

@@ -1,4 +1,5 @@
 path = require 'path'
+fs = require 'fs-plus'
 ModuleCache = require '../../src/module-cache'
 
 module.exports = (grunt) ->
@@ -26,4 +27,23 @@ module.exports = (grunt) ->
           'vendor'
         ]
 
+    validExtensions = ['.js', '.coffee', '.json', '.node']
+
+    extensions = {}
+    onFile = (filePath) ->
+      filePath = path.relative(appDir, filePath)
+      segments = filePath.split(path.sep)
+      return if segments.length > 1 and not (segments[0] in ['exports', 'node_modules', 'src', 'static', 'vendor'])
+
+      extension = path.extname(filePath)
+      if extension in validExtensions
+        extensions[extension] ?= []
+        extensions[extension].push(filePath)
+
+    onDirectory = -> true
+
+    files = fs.traverseTreeSync(appDir, onFile, onDirectory)
+
+    metadata._atomModuleCache.extensions = extensions
+
     grunt.file.write(path.join(appDir, 'package.json'), JSON.stringify(metadata, null, 2))

src/module-cache.coffee

@@ -83,6 +83,23 @@ satisfies = (version, rawRange) ->
     cache.ranges[rawRange] = parsedRange
   parsedRange.test(version)
 
+resolveFilePath = (relativePath, parentModule) ->
+  return unless relativePath
+  return unless parentModule?.id
+  return if relativePath[relativePath.length - 1] is '/'
+
+  resolvedPath = path.resolve(path.dirname(parentModule.id), relativePath)
+  if resolvedPath.indexOf(cache.resourcePath) is 0
+    extension = path.extname(resolvedPath)
+    if extension
+      return resolvedPath if cache.extensions[extension]?.has(resolvedPath)
+    else
+      for extension, paths of cache.extensions
+        resolvedPathWithExtension = "#{resolvedPath}#{extension}"
+        return resolvedPathWithExtension if paths.has(resolvedPathWithExtension)
+
+  return
+
 getCachedModulePath = (relativePath, parentModule) ->
   return unless relativePath
   return unless parentModule?.id
@@ -129,6 +146,7 @@ if cache.debug
   Module._findPath = (request, paths) ->
     cacheKey = JSON.stringify({request, paths})
     cache.findPathCount++ unless Module._pathCache[cacheKey]
+
     startTime = Date.now()
     foundPath = originalFindPath.apply(global, arguments)
     cache.findPathTime += Date.now() - startTime
@@ -158,6 +176,7 @@ exports.register = (resourcePath) ->
   originalResolveFilename = Module._resolveFilename
   Module._resolveFilename = (relativePath, parentModule) ->
     resolvedPath = getCachedModulePath(relativePath, parentModule)
+    resolvedPath ?= resolveFilePath(relativePath, parentModule)
     resolvedPath ? originalResolveFilename(relativePath, parentModule)
 
   cache.registered = true
@@ -181,6 +200,12 @@ exports.add = (directoryPath, metadata) ->
     for folderPath in entry.paths
       cache.folders[path.join(directoryPath, folderPath)] = entry.dependencies
 
+  if directoryPath is cache.resourcePath
+    for extension, paths of cacheToAdd?.extensions
+      cache.extensions[extension] ?= new Set()
+      for filePath in paths
+        cache.extensions[extension].add(path.join(directoryPath, filePath))
+
   return
 
 exports.cache = cache