Implement feature to ignore YAML files that parse to equivalent objects

Author: Kevin Paulisse

lib/octocatalog-diff/catalog-diff/differ.rb

@@ -5,6 +5,7 @@
 require 'json'
 require 'set'
 require 'stringio'
+require 'yaml'
 
 require_relative '../catalog'
 
@@ -153,6 +154,11 @@ def catdiff
         # out any such parameters from the result array.
         filter_diffs_for_absent_files(result) if @opts[:suppress_absent_file_details]
 
+        # If --ignore-equivalent-yaml-files is specified, then for any YAML file that is changed, parse the YAML
+        # to construct the object. If the objects are identical this means the YAML file differs only in whitespace
+        # or comments but not in function. Remove these.
+        filter_diffs_for_equivalent_yaml_files(result) if @opts[:ignore_equivalent_yaml_files]
+
         # That's it!
         @logger.debug "Exiting catdiff; change count: #{result.size}"
         result
@@ -165,6 +171,33 @@ def filter_diffs_for_ignored_items(result)
         result.reject! { |item| ignored?(item) }
       end
 
+      # To ignore YAML file differences that are only due to whitespace or comments (i.e., the YAML files themselves
+      # are functionally equivalent), parse the YAML content from both catalogs and compare objects. Remove when
+      # objects are identical.
+      # @param result [Array] Full result array (modified by this method)
+      def filter_diffs_for_equivalent_yaml_files(result)
+        result.reject! { |item| equivalent_yaml_files?(item) }
+      end
+
+      # Actually do the comparison of YAML objects for appropriate resources.
+      # @param diff [Array] Difference
+      # @return [Boolean] true if this difference is a YAML file with identical objects, false otherwise
+      def equivalent_yaml_files?(diff)
+        # Skip additions or removals - focus only on changes
+        return false unless diff[0] == '~' || diff[0] == '!'
+
+        # Make sure we are comparing file content for a file ending in .yaml or .yml extension
+        return false unless diff[1] =~ /^File\f.+\.ya?ml\fparameters\fcontent$/
+
+        # Attempt to convert the old (diff[2]) and new (diff[3]) into YAML objects. Assuming
+        # that doesn't error out, the return value is whether or not they're equal.
+        obj_old = YAML.load(diff[2])
+        obj_new = YAML.load(diff[3])
+        obj_old == obj_new
+      rescue # Rescue everything - if something failed, we aren't sure what's going on, so we'll return false.
+        false
+      end
+
       # If a file has ensure => absent, there are certain parameters that don't matter anymore. Filter
       # out any such parameters from the result array.
       # @param result [Array] Diff result list (modified by this method)