Ruby CLI: Support stdin as an option for [file] (#1186)

This pull request updates the Ruby CLI to accept `stdin` as an option
for all commands that accept `[file]`.

Now, the following is supported:
```bash
echo "<div>Hello</div>" | herb lex
cat file.html.erb | herb parse
```

You can also use `-` to explicitly read from stdin:
```bash
herb compile -
```

Resolves #1180

Author: marcoroth

lib/herb/cli.rb

@@ -13,11 +13,11 @@ class Herb::CLI
   def initialize(args)
     @args = args
     @command = args[0]
-    @file = args[1]
   end
 
   def call
     options
+    @file = @args[1]
 
     if silent
       if result.failed?
@@ -61,16 +61,23 @@ def directory
   end
 
   def file_content
-    if @file && File.exist?(@file)
+    if @file && @file != "-" && File.exist?(@file)
       File.read(@file)
-    elsif @file
+    elsif @file && @file != "-"
       puts "File doesn't exist: #{@file}"
       exit(1)
+    elsif @file == "-" || !$stdin.tty?
+      $stdin.read
     else
       puts "No file provided."
       puts
       puts "Usage:"
       puts "  bundle exec herb #{@command} [file] [options]"
+      puts
+      puts "You can also pipe content via stdin:"
+      puts "  echo \"<div>Hello</div>\" | bundle exec herb #{@command}"
+      puts "  cat file.html.erb | bundle exec herb #{@command}"
+      puts "  bundle exec herb #{@command} -"
       exit(1)
     end
   end
@@ -100,6 +107,14 @@ def help(exit_code = 0)
         bundle exec herb playground [file]  Open the content of the source file in the playground
         bundle exec herb version            Prints the versions of the Herb gem and the libherb library.
 
+      stdin:
+        Commands that accept [file] also accept input via stdin:
+          echo "<div>Hello</div>" | bundle exec herb lex
+          cat file.html.erb | bundle exec herb parse
+
+        Use `-` to explicitly read from stdin:
+          bundle exec herb compile -
+
       Options:
         #{option_parser.to_s.strip.gsub(/^    /, "  ")}
 

test/engine/cli_stdin_test.rb

@@ -0,0 +1,116 @@
+# frozen_string_literal: true
+
+require "English"
+require_relative "../test_helper"
+
+require "tempfile"
+require "json"
+
+module Engine
+  class CLIStdinTest < Minitest::Spec
+    def setup
+      skip "Shell stdin tests are skipped in CI" if ENV["CI"]
+    end
+
+    def with_temp_file(content)
+      file = Tempfile.new(["test_template", ".erb"])
+      file.write(content)
+      file.close
+      yield file.path
+    ensure
+      file&.unlink
+    end
+
+    test "shell: lex accepts piped stdin" do
+      output = `echo '<div>Hello</div>' | bundle exec herb lex 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "TOKEN_HTML_TAG_START"
+      assert_includes output, "div"
+    end
+
+    test "shell: parse accepts piped stdin" do
+      output = `echo '<div>Hello</div>' | bundle exec herb parse 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "DocumentNode"
+      assert_includes output, "HTMLElementNode"
+    end
+
+    test "shell: compile accepts piped stdin" do
+      output = `echo '<div><%= name %></div>' | bundle exec herb compile 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "_buf = ::String.new"
+      assert_includes output, "__herb.h((name))"
+    end
+
+    test "shell: ruby accepts piped stdin" do
+      output = `echo '<div><%= user.name %></div>' | bundle exec herb ruby 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "user.name"
+    end
+
+    test "shell: html accepts piped stdin" do
+      output = `echo '<div><%= user.name %></div>' | bundle exec herb html 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "<div>"
+      assert_includes output, "</div>"
+    end
+
+    test "shell: render accepts piped stdin" do
+      output = `echo '<div>Static</div>' | bundle exec herb render 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "<div>Static</div>"
+    end
+
+    test "shell: compile with json flag and stdin" do
+      output = `echo '<div>Test</div>' | bundle exec herb compile --json 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      json_data = JSON.parse(output)
+      assert_equal true, json_data["success"]
+      assert_includes json_data["source"], "_buf = ::String.new"
+    end
+
+    test "shell: lex with json flag and stdin" do
+      output = `echo '<div>Test</div>' | bundle exec herb lex --json 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      json_data = JSON.parse(output)
+      assert_kind_of Array, json_data
+      assert(json_data.any? { |token| token["type"] == "TOKEN_HTML_TAG_START" })
+    end
+
+    test "shell: compile with multiple flags and stdin" do
+      output = `echo '<div><%= x %></div>' | bundle exec herb compile --no-escape --freeze 2>&1`
+
+      assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+      assert_includes output, "# frozen_string_literal: true"
+      assert_includes output, "(x).to_s"
+    end
+
+    test "shell: stdin with file redirection and dash" do
+      with_temp_file("<article>Content</article>") do |file_path|
+        output = `bundle exec herb lex - < #{file_path} 2>&1`
+
+        assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+        assert_includes output, "TOKEN_HTML_TAG_START"
+        assert_includes output, "article"
+      end
+    end
+
+    test "shell: cat pipe to lex" do
+      with_temp_file("<section>Data</section>") do |file_path|
+        output = `cat #{file_path} | bundle exec herb lex 2>&1`
+
+        assert $CHILD_STATUS.success?, "Command failed with: #{output}"
+        assert_includes output, "TOKEN_HTML_TAG_START"
+        assert_includes output, "section"
+      end
+    end
+  end
+end

test/engine/cli_test.rb

@@ -38,6 +38,14 @@ def with_temp_file(content)
       file&.unlink
     end
 
+    def with_stdin(content)
+      original_stdin = $stdin
+      $stdin = StringIO.new(content)
+      yield
+    ensure
+      $stdin = original_stdin
+    end
+
     test "compile valid template" do
       template = "<div>Hello <%= name %>!</div>"
 
@@ -188,13 +196,22 @@ def with_temp_file(content)
     end
 
     test "compile no file provided" do
-      assert_raises(SystemExit) do
-        Herb::CLI.new(["compile"]).call
-      end
+      original_stdin = $stdin
+      mock_stdin = StringIO.new
+      def mock_stdin.tty? = true
+      $stdin = mock_stdin
 
-      output = captured_output
-      assert_includes output, "No file provided"
-      assert_includes output, "Usage:"
+      begin
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["compile"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "No file provided"
+        assert_includes output, "Usage:"
+      ensure
+        $stdin = original_stdin
+      end
     end
 
     test "help includes compile command" do
@@ -309,5 +326,163 @@ def with_temp_file(content)
       assert_includes output, "Unknown command"
       assert_includes output, "compile [file]"
     end
+
+    test "lex reads from stdin with dash argument" do
+      template = "<div>Hello</div>"
+
+      with_stdin(template) do
+        Herb::CLI.new(["lex", "-"]).call
+
+        output = captured_output
+        assert_includes output, "TOKEN_HTML_TAG_START"
+        assert_includes output, "TOKEN_IDENTIFIER"
+        assert_includes output, "div"
+      end
+    end
+
+    test "parse reads from stdin with dash argument" do
+      template = "<div>Hello</div>"
+
+      with_stdin(template) do
+        Herb::CLI.new(["parse", "-"]).call
+
+        output = captured_output
+        assert_includes output, "DocumentNode"
+        assert_includes output, "HTMLElementNode"
+        assert_includes output, "div"
+      end
+    end
+
+    test "compile reads from stdin with dash argument" do
+      template = "<div><%= name %></div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["compile", "-"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "_buf = ::String.new"
+        assert_includes output, "<div>"
+        assert_includes output, "__herb.h((name))"
+      end
+    end
+
+    test "ruby reads from stdin with dash argument" do
+      template = "<div><%= user.name %></div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["ruby", "-"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "user.name"
+      end
+    end
+
+    test "html reads from stdin with dash argument" do
+      template = "<div><%= user.name %></div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["html", "-"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "<div>"
+        assert_includes output, "</div>"
+      end
+    end
+
+    test "stdin with json output" do
+      template = "<div>Hello</div>"
+
+      with_stdin(template) do
+        Herb::CLI.new(["lex", "-", "--json"]).call
+
+        output = captured_output
+        json_data = JSON.parse(output)
+
+        assert_kind_of Array, json_data
+        assert(json_data.any? { |token| token["type"] == "TOKEN_HTML_TAG_START" })
+        assert(json_data.any? { |token| token["value"] == "div" })
+      end
+    end
+
+    test "compile stdin with json output" do
+      template = "<div><%= title %></div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["compile", "-", "--json"]).call
+        end
+
+        output = captured_output
+        json_data = JSON.parse(output)
+
+        assert_equal true, json_data["success"]
+        assert_includes json_data["source"], "_buf = ::String.new"
+        assert_equal "-", json_data["filename"]
+      end
+    end
+
+    test "compile stdin with options" do
+      template = "<div><%= user_input %></div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["compile", "-", "--no-escape", "--freeze"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "# frozen_string_literal: true"
+        assert_includes output, "(user_input).to_s"
+        refute_includes output, "__herb.h("
+      end
+    end
+
+    test "render reads from stdin" do
+      template = "<div>Rendered content</div>"
+
+      with_stdin(template) do
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["render", "-"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "<div>Rendered content</div>"
+      end
+    end
+
+    test "help includes stdin documentation" do
+      assert_raises(SystemExit) do
+        Herb::CLI.new(["help"]).call
+      end
+
+      output = captured_output
+      assert_includes output, "stdin:"
+      assert_includes output, "echo"
+      assert_includes output, "cat"
+    end
+
+    test "no file provided message includes stdin hint" do
+      original_stdin = $stdin
+      mock_stdin = StringIO.new
+      def mock_stdin.tty? = true
+      $stdin = mock_stdin
+
+      begin
+        assert_raises(SystemExit) do
+          Herb::CLI.new(["compile"]).call
+        end
+
+        output = captured_output
+        assert_includes output, "No file provided"
+        assert_includes output, "pipe content via stdin"
+      ensure
+        $stdin = original_stdin
+      end
+    end
   end
 end