language/node: set cache config via argument

instead of writing a .npmrc file, which simplifies the code.
npm_cache_config is still preserved for backwarts compatiblility and
usage int he kibana@n formulas in core.

Library/Homebrew/language/node.rb

@@ -1,7 +1,7 @@
 module Language
   module Node
     def self.npm_cache_config
-      "cache=#{HOMEBREW_CACHE}/npm_cache\n"
+      "cache=#{HOMEBREW_CACHE}/npm_cache"
     end
 
     def self.pack_for_installation
@@ -20,13 +20,9 @@ module Language
     end
 
     def self.setup_npm_environment
-      npmrc = Pathname.new("#{ENV["HOME"]}/.npmrc")
-      # only run setup_npm_environment once per formula
-      return if npmrc.exist?
-      # explicitly set npm's cache path to HOMEBREW_CACHE/npm_cache to fix
-      # issues caused by overriding $HOME (long build times, high disk usage)
-      # https://github.com/Homebrew/brew/pull/37#issuecomment-208840366
-      npmrc.write npm_cache_config
+      # guard that this is only run once
+      return if @env_set
+      @env_set = true
       # explicitly use our npm and node-gyp executables instead of the user
       # managed ones in HOMEBREW_PREFIX/lib/node_modules which might be broken
       begin
@@ -49,6 +45,7 @@ module Language
         -ddd
         --global
         --build-from-source
+        --#{npm_cache_config}
         --prefix=#{libexec}
         #{Dir.pwd}/#{pack}
       ]
@@ -57,9 +54,10 @@ module Language
     def self.local_npm_install_args
       setup_npm_environment
       # npm install args for local style module format
-      %w[
+      %W[
         -ddd
         --build-from-source
+        --#{npm_cache_config}
       ]
     end
   end

Library/Homebrew/test/language/node_spec.rb

@@ -2,22 +2,21 @@ require "language/node"
 
 describe Language::Node do
   describe "#setup_npm_environment" do
-    it "does nothing when npmrc exists" do
-      expect(subject.setup_npm_environment).to be_nil
-    end
-
-    it "calls prepend_path when node formula exists and npmrc does not exist" do
+    it "calls prepend_path when node formula exists only during the first call" do
       node = formula "node" do
         url "node-test"
       end
       stub_formula_loader(node)
-      allow_any_instance_of(Pathname).to receive(:exist?).and_return(false)
       expect(ENV).to receive(:prepend_path)
-      subject.setup_npm_environment
+      subject.instance_variable_set(:@env_set, false)
+      expect(subject.setup_npm_environment).to be_nil
+
+      expect(subject.instance_variable_get(:@env_set)).to eq(true)
+      expect(ENV).not_to receive(:prepend_path)
+      expect(subject.setup_npm_environment).to be_nil
     end
 
-    it "does not call prepend_path when node formula does not exist but npmrc exists" do
-      allow_any_instance_of(Pathname).to receive(:exist?).and_return(false)
+    it "does not call prepend_path when node formula does not exist" do
       expect(subject.setup_npm_environment).to be_nil
     end
   end
@@ -51,6 +50,6 @@ describe Language::Node do
 
   specify "#local_npm_install_args" do
     resp = subject.local_npm_install_args
-    expect(resp).to include("-ddd", "--build-from-source")
+    expect(resp).to include("-ddd", "--build-from-source", "--cache=#{HOMEBREW_CACHE}/npm_cache")
   end
 end