Add the ability to use variables in Gemfiles (#223)

This allows us to add custom instructions, or adding `frozen_string_literal` when desired.

README.md

@@ -159,6 +159,15 @@ customizations include:
 - heading: a string that by default adds "# This file was generated by Appraisal" to the top of each Gemfile, (the string will be commented for you)
 - single_quotes: a boolean that controls if strings are single quoted in each Gemfile, defaults to false
 
+You can also provide variables for substitution in the heading, based on each appraisal. Currently supported variables:
+- `%{appraisal}`: Becomes the name of each appraisal, e.g. `rails-3`
+- `%{gemfile}`: Becomes the filename of each gemfile, e.g. `rails-3.gemfile`
+- `%{gemfile_path}`: Becomes the full path of each gemfile, e.g. `/path/to/project/gemfiles/rails-3.gemfile`
+- `%{lockfile}`: Becomes the filename of each lockfile, e.g. `rails-3.gemfile.lock`
+- `%{lockfile_path}`: Becomes the full path of each lockfile, e.g. `/path/to/project/gemfiles/rails-3.gemfile.lock`
+- `%{relative_gemfile_path}`: Becomes the relative path of each gemfile, e.g. `gemfiles/rails-3.gemfile`
+- `%{relative_lockfile_path}`: Becomes the relative path of each lockfile, e.g. `gemfiles/rails-3.gemfile.lock`
+
 ### Example Usage
 
 **Appraisals**
@@ -169,8 +178,8 @@ customize_gemfiles do
     heading: <<~HEADING
       frozen_string_literal: true
 
-      File has been generated by Appraisal, do NOT modify it directly!
-      See the conventions at https://example.com/
+      `%{gemfile}` has been generated by Appraisal, do NOT modify it or `%{lockfile}` directly!
+      Make the changes to the "%{appraisal}" block in `Appraisals` instead. See the conventions at https://example.com/
     HEADING
   }
 end
@@ -184,8 +193,8 @@ Using the `Appraisals` file defined above, this is what the resulting `Gemfile`
 ```ruby
 # frozen_string_literal: true
 
-# File has been generated by Appraisal, do NOT modify it directly!
-# See the conventions at https://example.com/
+# `rails-3.gemfile` has been generated by Appraisal, do NOT modify it or `rails-3.gemfile.lock` directly!
+# Make the changes to the "rails-3" block in `Appraisals` instead. See the conventions at https://example.com/
 
 gem 'rails', '3.2.14'
 ```

lib/appraisal/appraisal.rb

@@ -63,7 +63,8 @@ def git_source(*args, &block)
 
     def write_gemfile
       File.open(gemfile_path, "w") do |file|
-        signature = Customize.heading || "This file was generated by Appraisal"
+        signature =
+          Customize.heading(self) || "This file was generated by Appraisal"
         file.puts([comment_lines(signature), quoted_gemfile].join("\n\n"))
       end
     end

lib/appraisal/customize.rb

@@ -5,12 +5,30 @@ def initialize(heading: nil, single_quotes: false)
       @@single_quotes = single_quotes
     end
 
-    def self.heading
+    def self.heading(gemfile)
       @@heading ||= nil
+      customize(@@heading, gemfile)
     end
 
     def self.single_quotes
       @@single_quotes ||= false
     end
+
+    def self.customize(heading, gemfile)
+      return nil unless heading
+
+      format(
+        heading.to_s,
+        appraisal: gemfile.send("clean_name"),
+        gemfile: gemfile.send("gemfile_name"),
+        gemfile_path: gemfile.gemfile_path,
+        lockfile: "#{gemfile.send('gemfile_name')}.lock",
+        lockfile_path: gemfile.send("lockfile_path"),
+        relative_gemfile_path: gemfile.relative_gemfile_path,
+        relative_lockfile_path: "#{gemfile.relative_gemfile_path}.lock",
+      )
+    end
+
+    private_class_method :customize
   end
 end

spec/appraisal/customize_spec.rb

@@ -1,18 +1,139 @@
 require "spec_helper"
+require "appraisal/appraisal"
 require "appraisal/customize"
 
 describe Appraisal::Customize do
-  it "has defaults" do
-    expect(described_class.heading).to eq nil
-    expect(described_class.single_quotes).to eq false
-    expect { described_class.new }.to_not(change do
-      [described_class.heading, described_class.single_quotes]
-    end)
+  let(:appraisal) { Appraisal::Appraisal.new("test", "Gemfile") }
+  let(:single_line_heading) { "This file was generated with a custom heading!" }
+  let(:multi_line_heading) do
+    <<~HEADING
+      frozen_string_literal: true
+
+      This file was generated with a custom heading!
+    HEADING
+  end
+  let(:subject) { described_class.new }
+  let(:single_line_subject) do
+    described_class.new(heading: single_line_heading)
+  end
+  let(:multi_line_single_quotes_subject) do
+    described_class.new(heading: multi_line_heading, single_quotes: true)
+  end
+
+  describe ".heading" do
+    it "returns nil if no heading is set" do
+      subject
+      expect(described_class.heading(appraisal)).to eq(nil)
+    end
+
+    it "returns the heading if set" do
+      single_line_subject
+      expect(described_class.heading(appraisal)).to eq(single_line_heading)
+    end
+
+    it "returns the heading without an trailing newline" do
+      multi_line_single_quotes_subject
+      expect(described_class.heading(appraisal)).to eq(multi_line_heading.chomp)
+      expect(described_class.heading(appraisal)).to_not end_with("\n")
+    end
+  end
+
+  describe ".single_quotes" do
+    it "returns false if not set" do
+      subject
+      expect(described_class.single_quotes).to eq(false)
+    end
+
+    it "returns true if set" do
+      multi_line_single_quotes_subject
+      expect(described_class.single_quotes).to eq(true)
+    end
   end
 
-  it "can override defaults" do
-    described_class.new(single_quotes: true, heading: "foo")
-    expect(described_class.heading).to eq "foo"
-    expect(described_class.single_quotes).to eq true
+  describe ".customize" do
+    let(:appraisal_name) { "test" }
+    let(:gemfile) { "test.gemfile" }
+    let(:lockfile) { "#{gemfile}.lock" }
+    let(:gemfile_relative_path) { "gemfiles/#{gemfile}" }
+    let(:lockfile_relative_path) { "gemfiles/#{lockfile}" }
+    let(:gemfile_full_path) { "/path/to/project/#{gemfile_relative_path}" }
+    let(:lockfile_full_path) { "/path/to/project/#{lockfile_relative_path}" }
+    before do
+      allow(appraisal).to receive(:gemfile_name).and_return(gemfile)
+      allow(appraisal).to receive(:gemfile_path).and_return(gemfile_full_path)
+      allow(appraisal).to receive(:lockfile_path).and_return(lockfile_full_path)
+      allow(appraisal).to receive(:relative_gemfile_path).
+        and_return(gemfile_relative_path)
+    end
+
+    it "returns nil if no heading is set" do
+      subject
+      expect(described_class.send(:customize, nil, appraisal)).to eq(nil)
+    end
+
+    it "returns the heading unchanged" do
+      single_line_subject
+      expect(described_class.send(
+               :customize,
+               single_line_heading,
+               appraisal,
+             )).to eq(single_line_heading)
+    end
+
+    it "returns the heading with the appraisal name" do
+      expect(described_class.send(
+               :customize,
+               "Appraisal: %{appraisal}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Appraisal: #{appraisal_name}")
+    end
+
+    it "returns the heading with the gemfile name" do
+      expect(described_class.send(
+               :customize,
+               "Gemfile: %{gemfile}", # rubocop:disable Style/FormatStringToken
+               appraisal,
+             )).to eq("Gemfile: #{gemfile}")
+    end
+
+    it "returns the heading with the gemfile path" do
+      expect(described_class.send(
+               :customize,
+               "Gemfile: %{gemfile_path}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Gemfile: #{gemfile_full_path}")
+    end
+
+    it "returns the heading with the lockfile name" do
+      expect(described_class.send(
+               :customize,
+               "Lockfile: %{lockfile}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Lockfile: #{lockfile}")
+    end
+
+    it "returns the heading with the lockfile path" do
+      expect(described_class.send(
+               :customize,
+               "Lockfile: %{lockfile_path}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Lockfile: #{lockfile_full_path}")
+    end
+
+    it "returns the heading with the relative gemfile path" do
+      expect(described_class.send(
+               :customize,
+               "Gemfile: %{relative_gemfile_path}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Gemfile: #{gemfile_relative_path}")
+    end
+
+    it "returns the heading with the relative lockfile path" do
+      expect(described_class.send(
+               :customize,
+               "Gemfile: %{relative_lockfile_path}", # rubocop:disable Style/FormatStringToken, Metrics/LineLength
+               appraisal,
+             )).to eq("Gemfile: #{lockfile_relative_path}")
+    end
   end
 end