feat: add package manager checker

Gemfile

@@ -3,3 +3,5 @@ source "https://rubygems.org"
 gemspec
 
 eval_gemfile File.expand_path("./Gemfile.development_dependencies", __dir__)
+
+gem "pry"

lib/shakapacker/instance.rb

@@ -1,4 +1,5 @@
 require "pathname"
+require "shakapacker/manager_checker"
 
 class Shakapacker::Instance
   cattr_accessor(:logger) { ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT)) }

lib/shakapacker/manager_checker.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+require "shakapacker/version"
+require "package_json"
+
+module Shakapacker
+  class ManagerChecker
+    class Error < StandardError; end
+
+    MANAGER_LOCKS = {
+      bun: "bun.lockb",
+      npm: "package-lock.json",
+      pnpm: "pnpm-lock.yaml",
+      yarn: "yarn.lock"
+    }
+
+    # Emits a warning if it's not obvious what package manager to use
+    def warn_unless_package_manager_is_obvious!
+      return if package_manager_set?
+
+      guessed_manager = guess_manager
+
+      return if guess_manager == :npm
+
+      Shakapacker.puts_deprecation_message(<<~MSG)
+        You have not got "packageManager" set in your package.json meaning that Shakapacker will use npm
+        but you've got a #{MANAGER_LOCKS[guessed_manager]} file meaning you probably want
+        to be using #{guessed_manager} instead.
+
+        To make this happen, set "packageManager" in your package.json to #{guessed_manager}@#{guess_manager_version}
+      MSG
+    end
+
+    def package_manager_set?
+      !PackageJson.read.fetch("packageManager", nil).nil?
+    end
+
+    def guess_manager_version
+      require "open3"
+
+      command = "#{guess_manager} --version"
+      stdout, stderr, status = Open3.capture3(command)
+
+      unless status.success?
+        raise Error, "#{command} failed with exit code #{status.exitstatus}: #{stderr}"
+      end
+
+      stdout.chomp
+    end
+
+    def guess_manager
+      MANAGER_LOCKS.find { |_, lock| File.exist?(lock) }&.first || :npm
+    end
+  end
+end

spec/shakapacker/manager_checker_spec.rb

@@ -0,0 +1,147 @@
+require_relative "spec_helper_initializer"
+require "shakapacker/version"
+
+Struct.new("Status", :exit_code) do
+  def success?
+    exit_code.zero?
+  end
+
+  def exitstatus
+    exit_code
+  end
+end
+
+def within_temp_directory(tmpdir = nil, &block)
+  Dir.mktmpdir("shakapacker-", tmpdir) do |dir|
+    Dir.chdir(dir, &block)
+  end
+end
+
+describe "ManagerChecker" do
+  around do |example|
+    within_temp_directory { example.run }
+  end
+
+  describe "#warn_unless_package_manager_is_obvious!" do
+    before do
+      allow(Shakapacker).to receive(:puts_deprecation_message)
+    end
+
+    context "when 'packageManager' is set in the package.json" do
+      before do
+        File.write("package.json", { "packageManager" => "pnpm" }.to_json)
+      end
+
+      it "does nothing" do
+        Shakapacker::ManagerChecker.new.warn_unless_package_manager_is_obvious!
+
+        expect(Shakapacker).not_to have_received(:puts_deprecation_message)
+      end
+    end
+
+    context "when the guessed manager is npm" do
+      it "does nothing" do
+        File.write("package.json", {}.to_json)
+        FileUtils.touch("package-lock.json")
+
+        Shakapacker::ManagerChecker.new.warn_unless_package_manager_is_obvious!
+
+        expect(Shakapacker).not_to have_received(:puts_deprecation_message)
+      end
+    end
+
+    Shakapacker::ManagerChecker::MANAGER_LOCKS.reject { |manager| manager == :npm }.each do |manager, lock|
+      context "when there is a #{lock}" do
+        before do
+          allow(Open3).to receive(:capture3).and_return(["1.2.3\n", "", Struct::Status.new(0)])
+        end
+
+        it "recommends setting 'packageManager' for #{manager}" do
+          File.write("package.json", {}.to_json)
+          FileUtils.touch(lock)
+
+          Shakapacker::ManagerChecker.new.warn_unless_package_manager_is_obvious!
+
+          expect(Shakapacker).to have_received(:puts_deprecation_message).with(<<~MSG)
+            You have not got "packageManager" set in your package.json meaning that Shakapacker will use npm
+            but you've got a #{lock} file meaning you probably want
+            to be using #{manager} instead.
+
+            To make this happen, set "packageManager" in your package.json to #{manager}@1.2.3
+          MSG
+        end
+      end
+    end
+  end
+
+  describe "#package_manager_set?" do
+    it "returns true when the 'packageManager' property is set" do
+      File.write("package.json", { "packageManager" => "npm" }.to_json)
+
+      expect(Shakapacker::ManagerChecker.new.package_manager_set?).to be true
+    end
+
+    it "returns false when the 'packageManager' property is not set" do
+      File.write("package.json", {}.to_json)
+
+      expect(Shakapacker::ManagerChecker.new.package_manager_set?).to be false
+    end
+  end
+
+  describe "#guess_manager_version" do
+    before do
+      allow(Open3).to receive(:capture3).and_return(["1.2.3\n", "", Struct::Status.new(0)])
+    end
+
+    Shakapacker::ManagerChecker::MANAGER_LOCKS.each do |manager, lock|
+      context "when a #{lock} exists" do
+        before { FileUtils.touch(lock) }
+
+        it "calls #{manager} with --version" do
+          Shakapacker::ManagerChecker.new.guess_manager_version
+
+          expect(Open3).to have_received(:capture3).with("#{manager} --version")
+        end
+      end
+    end
+
+    it "returns the output without a trailing newline" do
+      FileUtils.touch("package-lock.json")
+
+      expect(Shakapacker::ManagerChecker.new.guess_manager_version).to eq("1.2.3")
+    end
+
+    context "when the command errors" do
+      before do
+        allow(Open3).to receive(:capture3).and_return(["", "oh noes!", Struct::Status.new(1)])
+      end
+
+      it "raises an error" do
+        FileUtils.touch("package-lock.json")
+
+        expect { Shakapacker::ManagerChecker.new.guess_manager_version }.to raise_error(
+          Shakapacker::ManagerChecker::Error,
+          "npm --version failed with exit code 1: oh noes!"
+        )
+      end
+    end
+  end
+
+  describe "#guess_manager" do
+    Shakapacker::ManagerChecker::MANAGER_LOCKS.each do |manager, lock|
+      context "when a #{lock} exists" do
+        before { FileUtils.touch(lock) }
+
+        it "guesses #{manager}" do
+          expect(Shakapacker::ManagerChecker.new.guess_manager).to eq manager
+        end
+      end
+    end
+
+    context "when there is no lockfile" do
+      it "returns npm" do
+        expect(Shakapacker::ManagerChecker.new.guess_manager).to eq :npm
+      end
+    end
+  end
+end