Merge pull request #609 from alphagov/improve-packagecomponent

Make PackageContents regex more robust

Author: domoscargin

lib/package_contents.rb

@@ -1,22 +1,26 @@
 module PackageContents
+  SASS_IMPORT_PATTERN = %r{
+    ^\s*                       # leading whitespace
+    @(?:import|use)\s+         # @import or @use
+    ["']                       # opening quote
+      ([a-z-]+)                # capture the name
+      (?:/(?:_?index)          # optional /index or /_index
+        (?:\.scss)?            # optional .scss extension
+      )?
+    ["']                       # closing quote
+  }x
+
   def components
-    extract_from "components/_index.scss" do |line|
-      # Match anything found between `@import "` and `/index";`
-      line[/(?<=@import ")[a-z-]*(?=\/index";)/]
-    end
+    extract_from "components/_index.scss"
   end
 
   def overrides
-    extract_from "overrides/_index.scss" do |line|
-      # Match anything found between `@import "` and `";`
-      line[/(?<=@import ")[a-z-]*(?=";)/]
-    end
+    extract_from "overrides/_index.scss"
   end
 
-  def extract_from(file, &block)
+  def extract_from(file, pattern: SASS_IMPORT_PATTERN)
     File.readlines("node_modules/govuk-frontend/dist/govuk/#{file}")
-      .map(&block)
-      .compact
+      .filter_map { |line| line[pattern, 1] }
       .tap { |list| raise "No matches found in #{file}" if list.empty? }
   end
 end

spec/package_contents_spec.rb

@@ -9,55 +9,67 @@ class Test
     @helper = Test.new
   end
 
-  describe "#components" do
-    it "extracts components from components/_index.scss" do
+  shared_examples "a sass import extractor" do |method, file|
+    it "extracts names via @import" do
       allow(File).to receive(:readlines).and_return <<~FILE.split("\n")
         @import "../base";
 
-        @import "first-component/index";
-        @import "second-component/index";
-        @import "third-component/index";
+        @import "first";
+        @import "second/index";
+        @import "th-ird/_index";
+        @import "fourth/index.scss";
+        @import 'fifth/_index.scss';
+        // @import "false-match/index";
+        @import "";
       FILE
 
-      expect(@helper.components).to eq(%w[
-        first-component
-        second-component
-        third-component
+      expect(@helper.send(method)).to eq(%w[
+        first
+        second
+        th-ird
+        fourth
+        fifth
       ])
     end
 
-    it "throws if no components are found in components/_index.scss" do
-      allow(File).to receive(:readlines).and_return []
-
-      expect { @helper.components }.to raise_error(
-        "No matches found in components/_index.scss",
-      )
-    end
-  end
-
-  describe "#overrides" do
-    it "extracts overrides from overrides/_index.scss" do
+    it "extracts names via @use" do
       allow(File).to receive(:readlines).and_return <<~FILE.split("\n")
-        @import "../a-dependency";
+        @use "../base";
 
-        @import "one";
-        @import "two";
-        @import "th-ree";
+        @use "first";
+        @use "second/index";
+        @use "th-ird/_index";
+        @use "fourth/index.scss";
+        @use 'fifth/_index.scss';
+        @use "sixth" with ($config: true);
+        // @use "false-match/index";
+        @use "";
       FILE
 
-      expect(@helper.overrides).to eq(%w[
-        one
-        two
-        th-ree
+      expect(@helper.send(method)).to eq(%w[
+        first
+        second
+        th-ird
+        fourth
+        fifth
+        sixth
       ])
     end
 
-    it "throws if no overrides are found in components/_index.scss" do
+    it "throws if no matches are found" do
       allow(File).to receive(:readlines).and_return []
 
-      expect { @helper.overrides }.to raise_error(
-        "No matches found in overrides/_index.scss",
+      expect { @helper.send(method) }.to raise_error(
+        "No matches found in #{file}",
       )
     end
   end
+
+  describe "#components" do
+    it_behaves_like "a sass import extractor", :components, "components/_index.scss"
+  end
+
+  describe "#overrides" do
+    it_behaves_like "a sass import extractor", :overrides, "overrides/_index.scss"
+  end
 end