[fastlane] Print better errors when exception occurring in Fastfile (f…

…astlane#21977)

* Wrap error code content in codefences

* Better context for errors in Fastfile

fastlane/lib/fastlane/lane_manager_base.rb

@@ -78,15 +78,23 @@ def self.print_lane_context
     end
 
     def self.print_error_line(ex)
-      error_line = ex.backtrace.first
-      return if error_line.nil?
-
-      error_line = error_line.match("Fastfile:(\\d+):")
-      return unless error_line
+      lines = ex.backtrace_locations&.select { |loc| loc.path == 'Fastfile' }&.map(&:lineno)
+      return if lines.nil? || lines.empty?
+
+      fastfile_content = File.read(FastlaneCore::FastlaneFolder.fastfile_path, encoding: "utf-8")
+      if ex.backtrace_locations.first&.path == 'Fastfile'
+        # If exception happened directly in the Fastfile itself (e.g. ArgumentError)
+        UI.error("Error in your Fastfile at line #{lines.first}")
+        UI.content_error(fastfile_content, lines.first)
+        lines.shift
+      end
 
-      line = error_line[1]
-      UI.error("Error in your Fastfile at line #{line}")
-      UI.content_error(File.read(FastlaneCore::FastlaneFolder.fastfile_path, encoding: "utf-8"), line)
+      unless lines.empty?
+        # If exception happened directly in the Fastfile, also print the caller (still from the Fastfile).
+        # If exception happened in _fastlane_ internal code, print the line from the Fastfile that called it
+        UI.error("Called from Fastfile at line #{lines.first}")
+        UI.content_error(fastfile_content, lines.first)
+      end
     end
   end
 end

fastlane/lib/fastlane/runner.rb

@@ -40,13 +40,13 @@ def execute(lane, platform = nil, parameters = nil)
       return_val = nil
 
       path_to_use = FastlaneCore::FastlaneFolder.path || Dir.pwd
-      parameters ||= {}
+      parameters ||= {} # by default no parameters
       begin
         Dir.chdir(path_to_use) do # the file is located in the fastlane folder
           execute_flow_block(before_all_blocks, current_platform, current_lane, parameters)
           execute_flow_block(before_each_blocks, current_platform, current_lane, parameters)
 
-          return_val = lane_obj.call(parameters) # by default no parameters
+          return_val = lane_obj.call(parameters)
 
           # after blocks are only called if no exception was raised before
           # Call the platform specific after block and then the general one

fastlane_core/lib/fastlane_core/ui/implementations/shell.rb

@@ -108,12 +108,14 @@ def content_error(content, error_line)
       start_line = error_line - 2 < 1 ? 1 : error_line - 2
       end_line = error_line + 2 < contents.length ? error_line + 2 : contents.length
 
+      error('```')
       Range.new(start_line, end_line).each do |line|
         str = line == error_line ? " => " : "    "
         str << line.to_s.rjust(Math.log10(end_line) + 1)
         str << ":\t#{contents[line - 1]}"
         error(str)
       end
+      error('```')
     end
 
     #####################################################