Change npmSetup to install npm into the cache directory rather than n…

…ode_modles directory so that it's not deleted by yarn.

By this change, the npmSetup-installed npm is not deleted by npm with
shrinkwrap.

README.md

@@ -191,6 +191,9 @@ You can configure the plugin using the "node" extension block, like this:
       // Set the work directory for unpacking node
       workDir = file("${project.buildDir}/nodejs")
 
+      // Set the work directory for NPM
+      npmWorkDir = file("${project.buildDir}/npm")
+
       // Set the work directory for Yarn
       yarnWorkDir = file("${project.buildDir}/yarn")
 
@@ -203,13 +206,13 @@ You can configure the plugin using the "node" extension block, like this:
 Using a Custom (project-local) Version of `npm`
 -----------------------------------------------
 
-The plugin will use a locally-installed `npm` if it exists, regardless of the
-method of installation.
+If `npmVersion` is specified, the plugin installs that version of `npm` into `npmWorkDir`
+by the `npmSetup` task and use it.
+
+If `npmVersion` is not specified and a locally-installed `npm` exists, The plugin will
+use it.
 
-If you would like the plugin to install use a custom version of npm rather than
-the one bundled with the version of node installation, you can set `npmVersion`
-in the `node` extension block. The plugin will install the npm to the project's
-`node_modules` directory by configuring the `npmSetup` task.
+Otherwise, the plugin will use the `npm` bundled with the version of node installation.
 
 Using a Custom (project-local) Version of `yarn`
 -----------------------------------------------

src/integTest/groovy/com/moowork/gradle/node/NpmRule_integTest.groovy

@@ -43,39 +43,11 @@ class NpmRule_integTest
         copyResources( 'fixtures/npm-missing/package.json', 'package.json' )
 
         when:
-        def result = runTasksSuccessfully( 'npm_run_parent' )
+        def result = runTasksSuccessfully( 'npm_run_echoTest' )
 
         then:
         result.success
-        fileExists( 'child1.txt' )
-        fileExists( 'child2.txt' )
-        fileExists( 'parent1.txt' )
-        fileExists( 'parent2.txt' )
-    }
-
-    def 'fails to run npm module using npm_run_ when shrinkwrap removes local npm'()
-    {
-        given:
-        writeBuild( '''
-            apply plugin: 'com.moowork.node'
-
-            node {
-                version = "5.9.0"
-                npmVersion = "3.8.3"
-                download = true
-            }
-        ''' )
-
-        copyResources( 'fixtures/npm-missing/package.json', 'package.json' )
-        copyResources( 'fixtures/npm-missing/npm-shrinkwrap.json', 'npm-shrinkwrap.json' )
-
-        when:
-        def result = runTasksWithFailure( 'npm_run_parent' )
-
-        then:
-        result.failure != null
-        result.standardError.contains( 'Could not run npm command - local npm not found but requested in gradle node' )
-        result.standardError.contains( '3.8.3' )
+        fileExists( 'test.txt' )
     }
 
     def 'succeeds to run npm module using npm_run_ when shrinkwrap contains local npm'()