1 files changed, 141 insertions, 0 deletions
diff --git a/actionview/lib/action_view/template/error.rb b/actionview/lib/action_view/template/error.rb
new file mode 100644
index 0000000000..4e3c02e05e
--- /dev/null
+++ b/actionview/lib/action_view/template/error.rb
@@ -0,0 +1,141 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/enumerable"
+
+module ActionView
+  # = Action View Errors
+  class ActionViewError < StandardError #:nodoc:
+  end
+
+  class EncodingError < StandardError #:nodoc:
+  end
+
+  class WrongEncodingError < EncodingError #:nodoc:
+    def initialize(string, encoding)
+      @string, @encoding = string, encoding
+    end
+
+    def message
+      @string.force_encoding(Encoding::ASCII_8BIT)
+      "Your template was not saved as valid #{@encoding}. Please " \
+      "either specify #{@encoding} as the encoding for your template " \
+      "in your text editor, or mark the template with its " \
+      "encoding by inserting the following as the first line " \
+      "of the template:\n\n# encoding: <name of correct encoding>.\n\n" \
+      "The source of your template was:\n\n#{@string}"
+    end
+  end
+
+  class MissingTemplate < ActionViewError #:nodoc:
+    attr_reader :path
+
+    def initialize(paths, path, prefixes, partial, details, *)
+      @path = path
+      prefixes = Array(prefixes)
+      template_type = if partial
+        "partial"
+      elsif /layouts/i.match?(path)
+        "layout"
+      else
+        "template"
+      end
+
+      if partial && path.present?
+        path = path.sub(%r{([^/]+)$}, "_\\1")
+      end
+      searched_paths = prefixes.map { |prefix| [prefix, path].join("/") }
+
+      out  = "Missing #{template_type} #{searched_paths.join(", ")} with #{details.inspect}. Searched in:\n"
+      out += paths.compact.map { |p| "  * #{p.to_s.inspect}\n" }.join
+      super out
+    end
+  end
+
+  class Template
+    # The Template::Error exception is raised when the compilation or rendering of the template
+    # fails. This exception then gathers a bunch of intimate details and uses it to report a
+    # precise exception message.
+    class Error < ActionViewError #:nodoc:
+      SOURCE_CODE_RADIUS = 3
+
+      # Override to prevent #cause resetting during re-raise.
+      attr_reader :cause
+
+      def initialize(template)
+        super($!.message)
+        set_backtrace($!.backtrace)
+        @cause = $!
+        @template, @sub_templates = template, nil
+      end
+
+      def file_name
+        @template.identifier
+      end
+
+      def sub_template_message
+        if @sub_templates
+          "Trace of template inclusion: " +
+          @sub_templates.collect(&:inspect).join(", ")
+        else
+          ""
+        end
+      end
+
+      def source_extract(indentation = 0, output = :console)
+        return unless num = line_number
+        num = num.to_i
+
+        source_code = @template.source.split("\n")
+
+        start_on_line = [ num - SOURCE_CODE_RADIUS - 1, 0 ].max
+        end_on_line   = [ num + SOURCE_CODE_RADIUS - 1, source_code.length].min
+
+        indent = end_on_line.to_s.size + indentation
+        return unless source_code = source_code[start_on_line..end_on_line]
+
+        formatted_code_for(source_code, start_on_line, indent, output)
+      end
+
+      def sub_template_of(template_path)
+        @sub_templates ||= []
+        @sub_templates << template_path
+      end
+
+      def line_number
+        @line_number ||=
+          if file_name
+            regexp = /#{Regexp.escape File.basename(file_name)}:(\d+)/
+            $1 if message =~ regexp || backtrace.find { |line| line =~ regexp }
+          end
+      end
+
+      def annoted_source_code
+        source_extract(4)
+      end
+
+      private
+
+        def source_location
+          if line_number
+            "on line ##{line_number} of "
+          else
+            "in "
+          end + file_name
+        end
+
+        def formatted_code_for(source_code, line_counter, indent, output)
+          start_value = (output == :html) ? {} : []
+          source_code.inject(start_value) do |result, line|
+            line_counter += 1
+            if output == :html
+              result.update(line_counter.to_s => "%#{indent}s %s\n" % ["", line])
+            else
+              result << "%#{indent}s: %s" % [line_counter, line]
+            end
+          end
+        end
+    end
+  end
+
+  TemplateError = Template::Error
+end