Add strict locals linter

Author: simonlevasseur

lib/erb_lint/linters/strict_locals.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module ERBLint
+  module Linters
+    # Checks for final newlines at the end of a file.
+    class StrictLocals < Linter
+      include LinterRegistry
+
+      STRICT_LOCALS_REGEX = /\s+locals:\s+\((.*)\)/
+
+      def initialize(file_loader, config)
+        super
+      end
+
+      def run(processed_source)
+        file_content = processed_source.file_content
+        return if file_content.empty?
+
+        strict_locals_node = processed_source.ast.descendants(:erb).find do |erb_node|
+          indicator_node, _, code_node, _ = *erb_node
+
+          indicator_node_str = indicator_node&.deconstruct&.last
+          next unless indicator_node_str == "#"
+
+          code_node_str = code_node&.deconstruct&.last
+
+          code_node_str.match(STRICT_LOCALS_REGEX)
+        end
+
+        unless strict_locals_node
+          add_offense(
+            processed_source.to_source_range(0...processed_source.file_content.size),
+            <<~EOF.chomp,
+              Missing strict locals declaration.
+              Add <%# locals: () %> at the top of the file to enforce strict locals.
+            EOF
+          )
+        end
+      end
+
+      def autocorrect(_processed_source, offense)
+        lambda do |corrector|
+          corrector.insert_before(offense.source_range, "<%# locals: () %>\n")
+        end
+      end
+    end
+  end
+end

spec/erb_lint/linters/strict_locals_spec.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe ERBLint::Linters::StrictLocals do
+  let(:linter_config) { described_class.config_schema.new }
+  let(:file_loader) { ERBLint::FileLoader.new(".") }
+  let(:linter) { described_class.new(file_loader, linter_config) }
+  let(:processed_source) { ERBLint::ProcessedSource.new("file.html.erb", file) }
+
+  subject { linter.offenses }
+  before { linter.run(processed_source) }
+
+  context "when the ERB contains a strict locals declaration at the top of the file" do
+    let(:file) { <<~FILE }
+      <%# locals: (foo: "bar") %>
+      <div>
+        <%= foo %>
+      </div>
+    FILE
+
+    it "does not report any offenses" do
+      expect(subject.size).to(eq(0))
+    end
+  end
+
+  context "when the ERB contains a strict locals declaration anywhere else in the file" do
+    let(:file) { <<~FILE }
+      <div>
+        <%= foo %>
+      </div>
+      <%# locals: (foo: "bar") %>
+    FILE
+
+    it "does not report any offenses" do
+      expect(subject.size).to(eq(0))
+    end
+  end
+
+  context "when the ERB contains an empty strict locals declaration" do
+    let(:file) { <<~FILE }
+      <%# locals: () %>
+      <div>
+        <%= foo %>
+      </div>
+    FILE
+
+    it "does not report any offenses" do
+      expect(subject.size).to(eq(0))
+    end
+  end
+
+  context "when the ERB does not contain a strict locals declaration" do
+    let(:file) { <<~FILE }
+      <div>
+        <%= foo %>
+      </div>
+    FILE
+    let(:corrector) { ERBLint::Corrector.new(processed_source, subject) }
+    let(:corrected_content) { corrector.corrected_content }
+
+    it "reports an offense" do
+      expect(subject.size).to(eq(1))
+    end
+
+    it "reports the suggested fix" do
+      expect(subject.first.message).to(include(
+        "Missing strict locals declaration.\n",
+        "Add <%# locals: () %> at the top of the file to enforce strict locals.",
+      ))
+    end
+
+    it "corrects the file" do
+      expect(corrected_content).to(eq("<%# locals: () %>\n<div>\n  <%= foo %>\n</div>\n"))
+    end
+  end
+end