Make all pin* methods behave conventionally the same

README.md

@@ -211,6 +211,11 @@ module MyEngine
       app.config.importmap.paths << Engine.root.join("config/importmap.rb")
       # ...
     end
+
+    initializer "my-engine.javascript-assets" do |app|
+      app.config.assets.paths << File.expand_path("../../app/javascript")
+      # ...
+    end
   end
 end
 ```
@@ -220,7 +225,7 @@ And pinning JavaScript modules from the engine:
 ```ruby
 # my_engine/config/importmap.rb
 
-pin_all_from File.expand_path("../app/assets/javascripts", __dir__)
+pin_under "blorgh/application"
 ```
 
 

lib/importmap/map.rb

@@ -27,9 +27,9 @@ def pin(name, to: nil, preload: false)
     @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_under(under, inside: nil, preload: false)
     clear_cache
-    @directories[dir] = MappedDir.new(dir: dir, under: under, path: to, preload: preload)
+    @directories[under] = MappedDir.new(under: under, path: inside || under, preload: preload)
   end
 
   def preloaded_module_paths(resolver:)
@@ -71,7 +71,7 @@ def cache_sweeper(watches: nil)
   end
 
   private
-    MappedDir  = Struct.new(:dir, :path, :under, :preload, keyword_init: true)
+    MappedDir  = Struct.new(:under, :path, :preload, keyword_init: true)
     MappedFile = Struct.new(:name, :path, :preload, keyword_init: true)
 
     def cache_as(name)
@@ -116,9 +116,10 @@ def expanded_packages_and_directories
 
     def expand_directories_into(paths)
       @directories.values.each do |mapping|
-        if (absolute_path = absolute_root_of(mapping.dir)).exist?
-          find_javascript_files_in_tree(absolute_path).each do |filename|
-            module_filename = filename.relative_path_from(absolute_path)
+        unless (asset_path = asset_path_containing(mapping.path)).nil?
+          dir_path = asset_path.join(mapping.path)
+          find_javascript_files_in_tree(dir_path).each do |filename|
+            module_filename = filename.relative_path_from(dir_path)
             module_name     = module_name_from(module_filename, mapping)
             module_path     = module_path_from(module_filename, mapping)
 
@@ -133,14 +134,16 @@ def module_name_from(filename, mapping)
     end
 
     def module_path_from(filename, mapping)
-      [ mapping.path || mapping.under, filename.to_s ].compact.join("/")
+      [ mapping.path, filename.to_s ].compact.join("/")
     end
 
     def find_javascript_files_in_tree(path)
       Dir[path.join("**/*.js{,m}")].collect { |file| Pathname.new(file) }.select(&:file?)
     end
 
-    def absolute_root_of(path)
-      (pathname = Pathname.new(path)).absolute? ? pathname : Rails.root.join(path)
+    def asset_path_containing(path)
+      Rails.application.config.assets.paths.find do |asset_path|
+        Pathname.new(asset_path).join(path).directory?
+      end
     end
 end

test/dummy/config/importmap.rb

@@ -1,4 +1,2 @@
-pin_all_from "app/assets/javascripts"
-
 pin "md5", to: "https://cdn.skypack.dev/md5", preload: true
 pin "not_there", to: "nowhere.js"

test/importmap_test.rb

@@ -8,12 +8,11 @@ def setup
         pin "editor", to: "rich_text.js"
         pin "not_there", to: "nowhere.js"
         pin "md5", to: "https://cdn.skypack.dev/md5", preload: true
+        pin "my_lib", preload: true
 
-        pin_all_from "app/javascript/controllers", under: "controllers", preload: true
-        pin_all_from "app/javascript/spina/controllers", under: "controllers/spina", preload: true
-        pin_all_from "app/javascript/spina/controllers", under: "controllers/spina", to: "spina/controllers", preload: true
-        pin_all_from "app/javascript/helpers", under: "helpers", preload: true
-        pin_all_from "lib/assets/javascripts", preload: true
+        pin_under "controllers", preload: true
+        pin_under "controllers/spina", inside: "spina/controllers"
+        pin_under "helpers", inside: "helpers"
       end
     end
   end
@@ -30,32 +29,32 @@ def setup
     assert_nil generate_importmap_json["imports"]["not_there"]
   end
 
+  test "local pin for other folder" do
+    assert_match %r|assets/my_lib-.*\.js|, generate_importmap_json["imports"]["my_lib"]
+  end
+
   test "remote pin is not digest stamped" do
     assert_equal "https://cdn.skypack.dev/md5", generate_importmap_json["imports"]["md5"]
   end
 
-  test "directory pin mounted under matching subdir maps all files" do
+  test "directory pin with inferred inside" do
     assert_match %r|assets/controllers/goodbye_controller-.*\.js|, generate_importmap_json["imports"]["controllers/goodbye_controller"]
     assert_match %r|assets/controllers/utilities/md5_controller-.*\.js|, generate_importmap_json["imports"]["controllers/utilities/md5_controller"]
   end
 
-  test "directory pin mounted under matching subdir maps index as root" do
+  test "directory pin maps index as root" do
     assert_match %r|assets/controllers/index.*\.js|, generate_importmap_json["imports"]["controllers"]
   end
 
   test "directory pin mounted under matching subdir maps index as root at second depth" do
     assert_match %r|assets/helpers/requests/index.*\.js|, generate_importmap_json["imports"]["helpers/requests"]
   end
 
-  test "directory pin under custom asset path" do
+  test "directory pin with explicit inside" do
     assert_match %r|assets/spina/controllers/another_controller-.*\.js|, generate_importmap_json["imports"]["controllers/spina/another_controller"]
     assert_match %r|assets/spina/controllers/deeper/again_controller-.*\.js|, generate_importmap_json["imports"]["controllers/spina/deeper/again_controller"]
   end
 
-  test "directory pin without path or under" do
-    assert_match %r|assets/my_lib-.*\.js|, generate_importmap_json["imports"]["my_lib"]
-  end
-
   test "preloaded modules are included in preload tags" do
     preloading_module_paths = @importmap.preloaded_module_paths(resolver: ApplicationController.helpers).to_s
     assert_match /md5/, preloading_module_paths