Don't use cached less sources and imported files in dev mode

src/atom-environment.coffee

@@ -232,7 +232,7 @@ class AtomEnvironment extends Model
 
     @styles.initialize({@configDirPath})
     @packages.initialize({devMode, @configDirPath, resourcePath, safeMode})
-    @themes.initialize({@configDirPath, resourcePath, safeMode})
+    @themes.initialize({@configDirPath, resourcePath, safeMode, devMode})
 
     @commandInstaller.initialize(@getVersion())
     @workspace.initialize()

src/less-compile-cache.coffee

@@ -4,9 +4,9 @@ LessCache = require 'less-cache'
 # {LessCache} wrapper used by {ThemeManager} to read stylesheets.
 module.exports =
 class LessCompileCache
-  @cacheDir: path.join(process.env.ATOM_HOME, 'compile-cache', 'less')
-
   constructor: ({resourcePath, importPaths, lessSourcesByRelativeFilePath, importedFilePathsByRelativeImportPath}) ->
+    cacheDir = path.join(process.env.ATOM_HOME, 'compile-cache', 'less')
+
     @lessSearchPaths = [
       path.join(resourcePath, 'static', 'variables')
       path.join(resourcePath, 'static')
@@ -22,7 +22,7 @@ class LessCompileCache
       resourcePath,
       lessSourcesByRelativeFilePath,
       importedFilePathsByRelativeImportPath,
-      cacheDir: @constructor.cacheDir,
+      cacheDir,
       fallbackDir: path.join(resourcePath, 'less-compile-cache')
     })
 

src/theme-manager.coffee

@@ -3,6 +3,7 @@ _ = require 'underscore-plus'
 {Emitter, CompositeDisposable} = require 'event-kit'
 {File} = require 'pathwatcher'
 fs = require 'fs-plus'
+LessCompileCache = require './less-compile-cache'
 
 # Extended: Handles loading and activating available themes.
 #
@@ -18,16 +19,15 @@ class ThemeManager
     @packageManager.onDidActivateInitialPackages =>
       @onDidChangeActiveThemes => @packageManager.reloadActivePackageStyleSheets()
 
+  initialize: ({@resourcePath, @configDirPath, @safeMode, devMode}) ->
     @lessSourcesByRelativeFilePath = null
-    if typeof snapshotAuxiliaryData is 'undefined'
+    if devMode or typeof snapshotAuxiliaryData is 'undefined'
       @lessSourcesByRelativeFilePath = {}
       @importedFilePathsByRelativeImportPath = {}
     else
       @lessSourcesByRelativeFilePath = snapshotAuxiliaryData.lessSourcesByRelativeFilePath
       @importedFilePathsByRelativeImportPath = snapshotAuxiliaryData.importedFilePathsByRelativeImportPath
 
-  initialize: ({@resourcePath, @configDirPath, @safeMode}) ->
-
   ###
   Section: Event Subscription
   ###
@@ -202,14 +202,12 @@ class ThemeManager
       fs.readFileSync(stylesheetPath, 'utf8')
 
   loadLessStylesheet: (lessStylesheetPath, importFallbackVariables=false) ->
-    unless @lessCache?
-      LessCompileCache = require './less-compile-cache'
-      @lessCache = new LessCompileCache({
-        @resourcePath,
-        @lessSourcesByRelativeFilePath,
-        @importedFilePathsByRelativeImportPath,
-        importPaths: @getImportPaths()
-      })
+    @lessCache ?= new LessCompileCache({
+      @resourcePath,
+      @lessSourcesByRelativeFilePath,
+      @importedFilePathsByRelativeImportPath,
+      importPaths: @getImportPaths()
+    })
 
     try
       if importFallbackVariables