Set "trailing" on the comment node

Comment nodes can know if they are trailing comments by looking at the
previous token.  If we set this on the comment object then we don't need
to look at source slices when attaching comments

Author: tenderlove

ext/prism/extension.c

@@ -471,9 +471,12 @@ parser_location(const pm_parser_t *parser, VALUE source, bool freeze, const uint
  */
 static inline VALUE
 parser_comment(const pm_parser_t *parser, VALUE source, bool freeze, const pm_comment_t *comment) {
-    VALUE argv[] = { PARSER_LOCATION_LOC(parser, source, freeze, comment->location) };
+    VALUE argv[] = {
+        comment->trailing ? Qtrue : Qfalse,
+        PARSER_LOCATION_LOC(parser, source, freeze, comment->location)
+    };
     VALUE type = (comment->type == PM_COMMENT_EMBDOC) ? rb_cPrismEmbDocComment : rb_cPrismInlineComment;
-    return rb_class_new_instance_freeze(1, argv, type, freeze);
+    return rb_class_new_instance_freeze(2, argv, type, freeze);
 }
 
 /**

include/prism/parser.h

@@ -467,6 +467,8 @@ typedef struct pm_comment {
 
     /** The type of comment that we've found. */
     pm_comment_type_t type;
+
+    bool trailing;
 } pm_comment_t;
 
 /**

lib/prism/parse_result.rb

@@ -513,8 +513,15 @@ class Comment
     # The location of this comment in the source.
     attr_reader :location
 
+    # Returns true if this comment happens on the same line as other code and
+    # false if the comment is by itself.
+    def trailing?
+      @trailing
+    end
+
     # Create a new comment object with the given location.
-    def initialize(location)
+    def initialize(trailing, location)
+      @trailing = trailing
       @location = location
     end
 
@@ -532,12 +539,6 @@ def slice
   # InlineComment objects are the most common. They correspond to comments in
   # the source file like this one that start with #.
   class InlineComment < Comment
-    # Returns true if this comment happens on the same line as other code and
-    # false if the comment is by itself.
-    def trailing?
-      !location.start_line_slice.strip.empty?
-    end
-
     # Returns a string representation of this comment.
     def inspect
       "#<Prism::InlineComment @location=#{location.inspect}>"
@@ -547,11 +548,6 @@ def inspect
   # EmbDocComment objects correspond to comments that are surrounded by =begin
   # and =end.
   class EmbDocComment < Comment
-    # This can only be true for inline comments.
-    def trailing?
-      false
-    end
-
     # Returns a string representation of this comment.
     def inspect
       "#<Prism::EmbDocComment @location=#{location.inspect}>"

lib/prism/parse_result/comments.rb

@@ -122,7 +122,7 @@ def nearest_targets(node, comment)
         comment_end = comment.location.end_offset
 
         targets = [] #: Array[_Target]
-        node.comment_targets.map do |value|
+        node.comment_targets.each do |value|
           case value
           when StatementsNode
             targets.concat(value.body.map { |node| NodeTarget.new(node) })

src/prism.c

@@ -9291,12 +9291,13 @@ parser_lex_callback(pm_parser_t *parser) {
  * Return a new comment node of the specified type.
  */
 static inline pm_comment_t *
-parser_comment(pm_parser_t *parser, pm_comment_type_t type) {
+parser_comment(pm_parser_t *parser, pm_comment_type_t type, bool trailing) {
     pm_comment_t *comment = (pm_comment_t *) xcalloc(1, sizeof(pm_comment_t));
     if (comment == NULL) return NULL;
 
     *comment = (pm_comment_t) {
         .type = type,
+        .trailing = trailing,
         .location = { parser->current.start, parser->current.end }
     };
 
@@ -9324,7 +9325,7 @@ lex_embdoc(pm_parser_t *parser) {
     parser_lex_callback(parser);
 
     // Now, create a comment that is going to be attached to the parser.
-    pm_comment_t *comment = parser_comment(parser, PM_COMMENT_EMBDOC);
+    pm_comment_t *comment = parser_comment(parser, PM_COMMENT_EMBDOC, false);
     if (comment == NULL) return PM_TOKEN_EOF;
 
     // Now, loop until we find the end of the embedded documentation or the end
@@ -9831,7 +9832,11 @@ parser_lex(pm_parser_t *parser) {
                     // If we found a comment while lexing, then we're going to
                     // add it to the list of comments in the file and keep
                     // lexing.
-                    pm_comment_t *comment = parser_comment(parser, PM_COMMENT_INLINE);
+                    bool trailing = true;
+                    if (parser->previous.type == PM_TOKEN_EOF || parser->previous.type == PM_TOKEN_NEWLINE) {
+                        trailing = false;
+                    }
+                    pm_comment_t *comment = parser_comment(parser, PM_COMMENT_INLINE, trailing);
                     pm_list_append(&parser->comment_list, (pm_list_node_t *) comment);
 
                     if (ending) parser->current.end++;

templates/lib/prism/serialize.rb.erb

@@ -295,8 +295,8 @@ module Prism
           Array.new(load_varuint) do
             comment =
               case load_varuint
-              when 0 then InlineComment.new(load_location_object(freeze))
-              when 1 then EmbDocComment.new(load_location_object(freeze))
+              when 0 then InlineComment.new(load_boolean, load_location_object(freeze))
+              when 1 then EmbDocComment.new(load_boolean, load_location_object(freeze))
               end
 
             comment.freeze if freeze
@@ -450,6 +450,10 @@ module Prism
         value
       end
 
+      def load_boolean
+        io.getbyte != 0
+      end
+
       def load_double
         io.read(8).unpack1("D")
       end