Preload all by default (#218)

* Preload all by default

* Fix test fixtures

Author: dhh

README.md

@@ -115,20 +115,20 @@ Unpinning and removing "object-assign"
 
 ## Preloading pinned modules
 
-To avoid the waterfall effect where the browser has to load one file after another before it can get to the deepest nested import, importmap-rails supports [modulepreload links](https://developers.google.com/web/updates/2017/12/modulepreload). Pinned modules can be preloaded by appending `preload: true` to the pin.
+To avoid the waterfall effect where the browser has to load one file after another before it can get to the deepest nested import, importmap-rails uses [modulepreload links](https://developers.google.com/web/updates/2017/12/modulepreload) by default. If you don't want to preload a dependencies, because it'you want to load it on-demand for efficiency, pinned modules can prevent preloading by appending `preload: false` to the pin.
 
 Example:
 
 ```ruby
 # config/importmap.rb
-pin "@github/hotkey", to: "https://ga.jspm.io/npm:@github/hotkey@1.4.4/dist/index.js", preload: true
-pin "md5", to: "https://cdn.jsdelivr.net/npm/md5@2.3.0/md5.js"
+pin "@github/hotkey", to: "vendor/javascript/@github--hotkey.js"
+pin "md5", to: "vendor/javascript/md5.js", preload: false
 
 # app/views/layouts/application.html.erb
 <%= javascript_importmap_tags %>
 
 # will include the following link before the importmap is setup:
-<link rel="modulepreload" href="https://ga.jspm.io/npm:@github/hotkey@1.4.4/dist/index.js">
+<link rel="modulepreload" href="/assets/javascripts/@github--hotkey.js">
 ...
 ```
 
@@ -177,7 +177,7 @@ Pin your js file:
 ```rb
 # config/importmap.rb
 # ... other pins...
-pin "checkout"
+pin "checkout", preload: false
 ```
 
 Import your module on the specific page. Note: you'll likely want to use a `content_for` block on the specifc page/partial, then yield it in your layout.

lib/importmap/map.rb

@@ -25,12 +25,12 @@ def draw(path = nil, &block)
     self
   end
 
-  def pin(name, to: nil, preload: false)
+  def pin(name, to: nil, preload: true)
     clear_cache
     @packages[name] = MappedFile.new(name: name, path: to || "#{name}.js", preload: preload)
   end
 
-  def pin_all_from(dir, under: nil, to: nil, preload: false)
+  def pin_all_from(dir, under: nil, to: nil, preload: true)
     clear_cache
     @directories[dir] = MappedDir.new(dir: dir, under: under, path: to, preload: preload)
   end

test/dummy/config/importmap.rb

@@ -1,4 +1,4 @@
 pin_all_from "app/assets/javascripts"
 
 pin "md5", to: "https://cdn.skypack.dev/md5", preload: true
-pin "not_there", to: "nowhere.js"
+pin "not_there", to: "nowhere.js", preload: false

test/importmap_test.rb

@@ -4,9 +4,9 @@ class ImportmapTest < ActiveSupport::TestCase
   def setup
     @importmap = Importmap::Map.new.tap do |map|
       map.draw do
-        pin "application"
-        pin "editor", to: "rich_text.js"
-        pin "not_there", to: "nowhere.js"
+        pin "application", preload: false
+        pin "editor", to: "rich_text.js", preload: false
+        pin "not_there", to: "nowhere.js", preload: false
         pin "md5", to: "https://cdn.skypack.dev/md5", preload: true
 
         pin_all_from "app/javascript/controllers", under: "controllers", preload: true