katex.rb in katex-0.1.1

- old
+ new

@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 require 'katex/version'
 require 'katex/engine' if defined?(Rails)
 require 'execjs'
+require 'erb'
 
 # Provides a Ruby wrapper for KaTeX server-side rendering.
 module Katex
   @load_context_mutex = Mutex.new
   @context = nil
@@ -12,26 +13,44 @@
     # Renders the given math expression to HTML via katex.renderToString.
     #
     # @param math [String] The math (Latex) expression
     # @param display_mode [Boolean] Whether to render in display mode.
     # @param throw_on_error [Boolean] Whether to raise on error. If false,
-    #   renders the error message instead.
+    #   renders the error message instead (even in case of ParseError, unlike
+    #   the native katex).
+    # @param error_color [String] Error text CSS color.
     # @param render_options [Hash] Additional options for katex.renderToString.
     #   See https://github.com/Khan/KaTeX#rendering-options.
     # @return [String] HTML. If strings respond to html_safe, the result will be
     #   HTML-safe.
     # @note This method is thread-safe as long as your ExecJS runtime is
     #   thread-safe. MiniRacer is the recommended runtime.
-    def render(math, display_mode: false, throw_on_error: false,
-               **render_options)
-      result = katex_context.call(
-        'katex.renderToString',
-        math,
-        displayMode: display_mode,
-        throwOnError: throw_on_error,
-        **render_options
-      )
+    def render(math, display_mode: false, throw_on_error: true,
+               error_color: '#cc0000', macros: {}, **render_options)
+      begin
+        result = katex_context.call(
+            'katex.renderToString',
+            math,
+            displayMode: display_mode,
+            throwOnError: throw_on_error,
+            errorColor: error_color,
+            macros: macros,
+            **render_options
+        )
+      rescue ExecJS::ProgramError => e
+        raise e if throw_on_error
+        result = <<~HTML
+          <span class='katex'>
+            <span class='katex-html'>
+              <span style='color: #{error_color}'>
+                #{ERB::Util.h e.message.sub(/^ParseError: /, '')}
+              </span>
+            </span>
+          </span>
+        HTML
+      end
+
       result = result.html_safe if result.respond_to?(:html_safe)
       result
     end
 
     def katex_context
@@ -39,10 +58,10 @@
         @context ||= ExecJS.compile(File.read(katex_js_path))
       end
     end
 
     def katex_js_path
-      File.expand_path File.join('vendor', 'assets', 'javascripts', 'katex.js'),
+      File.expand_path File.join('vendor', 'katex', 'javascripts', 'katex.js'),
                        gem_path
     end
 
     def gem_path
       @gem_path ||=