fix: execute commands consistently for paths with spaces

Note that this is a pretty heavy refactoring, where code was moved
from `exe/tailwindcss` to `lib/tailwindcss/commands.rb` where we can
more easily run unit tests on it.

Note also that we no longer use Shellwords to build command strings, a
library which does not generate correct strings on Windows
platforms. Instead we consistently use arrays of command arguments,
which can be passed to `exec` or `system` however we see fit.

The wrapper script conditionally uses `system` on windows platforms
because `exec` can't find the executable (see related issue at
rubys/sprockets-esbuild#4).

Finally, note that the rake tasks no longer use the `exe/tailwindcss`
wrapper script, and instead use the binary executable directly. We can
reverse this decision if we ever decide to support manually-installed
tailwindcss somewhere on the $PATH; but because previously the rake
tasks hardcoded the path/to/exe/tailwindcss, we're not introducing any
new constraints by skipping the wrapper.

exe/tailwindcss

@@ -1,46 +1,19 @@
 #! /usr/bin/env ruby
 # because rubygems shims assume a gem's executables are Ruby
 
-require "shellwords"
-require "tailwindcss/upstream"
-
-supported_platforms = Tailwindcss::Upstream::NATIVE_PLATFORMS.keys
-platform = [:cpu, :os].map { |m| Gem::Platform.local.send(m) }.join("-")
-
-if supported_platforms.none? { |supported_platform| Gem::Platform.match(supported_platform) }
-  STDERR.puts(<<~ERRMSG)
-    ERROR: tailwindcss-rails does not support the #{platform} platform
-    Please install tailwindcss following instructions at https://tailwindcss.com/docs/installation
-  ERRMSG
+require "tailwindcss/commands"
+
+begin
+  command = [Tailwindcss::Commands.executable, *ARGV]
+  puts command.inspect
+  if Gem.win_platform?
+    # use system rather than exec as exec inexplicably fails to find the executable on Windows
+    # see related https://github.com/rubys/sprockets-esbuild/pull/4
+    system(*command, exception: true)
+  else
+    exec(*command)
+  end
+rescue Tailwindcss::Commands::UnsupportedPlatformException, Tailwindcss::Commands::ExecutableNotFoundException => e
+  STDERR.puts("ERROR: " + e.message)
   exit 1
 end
-
-exe_path = Dir.glob(File.join(__dir__, "*", "tailwindcss")).find do |f|
-  Gem::Platform.match(File.basename(File.dirname(f)))
-end
-if exe_path.nil?
-  STDERR.puts(<<~ERRMSG)
-    ERROR: Cannot find the tailwindcss executable for #{platform} in #{__dir__}
-    If you're using bundler, please make sure you're on the latest bundler version:
-
-      gem install bundler
-      bundle update --bundler
-
-    Then make sure your lock file includes this platform by running:
-
-      bundle lock --add-platform #{platform}
-      bundle install
-
-    See `bundle lock --help` output for details.
-        
-    If you're still seeing this message after taking those steps, try running
-    `bundle config` and ensure `force_ruby_platform` isn't set to `true`. See
-    https://github.com/rails/tailwindcss-rails#check-bundle_force_ruby_platform
-    for more details.
-  ERRMSG
-  exit 1
-end
-
-command = Shellwords.join([exe_path, ARGV].flatten)
-puts "+ #{command}"
-exec(command)

lib/tailwindcss-rails.rb

@@ -1,6 +1,7 @@
 module Tailwindcss
 end
 
-require "tailwindcss/upstream"
-require "tailwindcss/version"
-require "tailwindcss/engine"
+require_relative "tailwindcss/upstream"
+require_relative "tailwindcss/version"
+require_relative "tailwindcss/engine"
+require_relative "tailwindcss/commands"

lib/tailwindcss/commands.rb

@@ -0,0 +1,73 @@
+require_relative "upstream"
+
+module Tailwindcss
+  module Commands
+    # raised when the host platform is not supported by upstream tailwindcss's binary releases
+    class UnsupportedPlatformException < StandardError
+    end
+
+    # raised when the tailwindcss executable could not be found where we expected it to be
+    class ExecutableNotFoundException < StandardError
+    end
+
+    class << self
+      def platform
+        [:cpu, :os].map { |m| Gem::Platform.local.send(m) }.join("-")
+      end
+
+      def executable(
+        exe_path: File.expand_path(File.join(__dir__, "..", "..", "exe"))
+      )
+        if Tailwindcss::Upstream::NATIVE_PLATFORMS.keys.none? { |p| Gem::Platform.match(p) }
+          raise UnsupportedPlatformException, <<~MESSAGE
+            tailwindcss-rails does not support the #{platform} platform
+            Please install tailwindcss following instructions at https://tailwindcss.com/docs/installation
+          MESSAGE
+        end
+
+        exe_path = Dir.glob(File.expand_path(File.join(exe_path, "*", "tailwindcss"))).find do |f|
+          Gem::Platform.match(File.basename(File.dirname(f)))
+        end
+
+        if exe_path.nil?
+          raise ExecutableNotFoundException, <<~MESSAGE
+            Cannot find the tailwindcss executable for #{platform} in #{exe_path}
+
+            If you're using bundler, please make sure you're on the latest bundler version:
+
+                gem install bundler
+                bundle update --bundler
+
+            Then make sure your lock file includes this platform by running:
+
+                bundle lock --add-platform #{platform}
+                bundle install
+
+            See `bundle lock --help` output for details.
+
+            If you're still seeing this message after taking those steps, try running
+            `bundle config` and ensure `force_ruby_platform` isn't set to `true`. See
+            https://github.com/rails/tailwindcss-rails#check-bundle_force_ruby_platform
+            for more details.
+          MESSAGE
+        end
+
+        exe_path
+      end
+
+      def compile_command(**kwargs)
+        [
+          executable(**kwargs),
+          "-i", Rails.root.join("app/assets/stylesheets/application.tailwind.css").to_s,
+          "-o", Rails.root.join("app/assets/builds/tailwind.css").to_s,
+          "-c", Rails.root.join("config/tailwind.config.js").to_s,
+          "--minify",
+        ]
+      end
+
+      def watch_command(**kwargs)
+        compile_command(**kwargs) << "-w"
+      end
+    end
+  end
+end

lib/tasks/build.rake

@@ -1,14 +1,16 @@
-TAILWIND_COMPILE_COMMAND = "#{RbConfig.ruby} #{Pathname.new(__dir__).to_s}/../../exe/tailwindcss -i '#{Rails.root.join("app/assets/stylesheets/application.tailwind.css")}' -o '#{Rails.root.join("app/assets/builds/tailwind.css")}' -c '#{Rails.root.join("config/tailwind.config.js")}' --minify"
-
 namespace :tailwindcss do
   desc "Build your Tailwind CSS"
   task :build do
-    system(TAILWIND_COMPILE_COMMAND, exception: true)
+    command = Tailwindcss::Commands.compile_command
+    puts command.inspect
+    system(*command, exception: true)
   end
 
   desc "Watch and build your Tailwind CSS on file changes"
   task :watch do
-    system "#{TAILWIND_COMPILE_COMMAND} -w"
+    command = Tailwindcss::Commands.watch_command
+    puts command.inspect
+    system(*command)
   end
 end
 

test/lib/tailwindcss/commands_test.rb

@@ -0,0 +1,65 @@
+require "test_helper"
+require "minitest/mock"
+
+class Tailwindcss::CommandsTest < ActiveSupport::TestCase
+  test ".platform is a string containing just the cpu and os (not the version)" do
+    expected = "#{Gem::Platform.local.cpu}-#{Gem::Platform.local.os}"
+    assert_equal(expected, Tailwindcss::Commands.platform)
+  end
+
+  def mock_exe_directory(platform)
+    Dir.mktmpdir do |dir|
+      FileUtils.mkdir(File.join(dir, platform))
+      path = File.join(dir, platform, "tailwindcss")
+      FileUtils.touch(path)
+      Gem::Platform.stub(:match, true) do
+        yield(dir, path)
+      end
+    end
+  end
+
+  test ".executable returns the absolute path to the binary" do
+    mock_exe_directory("sparc-solaris2.8") do |dir, executable|
+      expected = File.expand_path(File.join(dir, "sparc-solaris2.8", "tailwindcss"))
+      assert_equal(expected, executable, "assert on setup")
+      assert_equal(expected, Tailwindcss::Commands.executable(exe_path: dir))
+    end
+  end
+
+  test ".executable raises UnsupportedPlatformException when we're not on a supported platform" do
+    Gem::Platform.stub(:match, false) do # nothing is supported
+      assert_raises(Tailwindcss::Commands::UnsupportedPlatformException) do
+        Tailwindcss::Commands.executable
+      end
+    end
+  end
+
+  test ".executable raises ExecutableNotFoundException when we can't find the executable we expect" do
+    Dir.mktmpdir do |dir| # empty directory
+      assert_raises(Tailwindcss::Commands::ExecutableNotFoundException) do
+        Tailwindcss::Commands.executable(exe_path: dir)
+      end
+    end
+  end
+
+  test ".compile_command" do
+    mock_exe_directory("sparc-solaris2.8") do |dir, executable|
+      Rails.stub(:root, File) do # Rails.root won't work in this test suite
+        actual = Tailwindcss::Commands.compile_command(exe_path: dir)
+        assert_kind_of(Array, actual)
+        assert_equal(executable, actual.first)
+      end
+    end
+  end
+
+  test ".watch_command" do
+    mock_exe_directory("sparc-solaris2.8") do |dir, executable|
+      Rails.stub(:root, File) do # Rails.root won't work in this test suite
+        actual = Tailwindcss::Commands.watch_command(exe_path: dir)
+        assert_kind_of(Array, actual)
+        assert_equal(executable, actual.first)
+        assert_includes(actual, "-w")
+      end
+    end
+  end
+end