Allow different line suffix nodes to have different priorities.

Author: kddnewton

CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 - Ensure comments on assignment after the `=` before the value keep their place.
 - Trailing comments on parameters with no parentheses now do not force a break.
 - Allow `ArrayLiteral` opening brackets to have trailing comments.
+- Allow different line suffix nodes to have different priorities.
 
 ### Changed
 

lib/syntax_tree.rb

@@ -113,6 +113,9 @@ def initialize(error, lineno, column)
   # A slightly enhanced PP that knows how to format recursively including
   # comments.
   class Formatter < PP
+    COMMENT_PRIORITY = 1
+    HEREDOC_PRIORITY = 2
+
     attr_reader :stack, :quote
 
     def initialize(*)
@@ -140,7 +143,7 @@ def format(node)
 
         # Print all comments that were found after the node.
         trailing.each do |comment|
-          line_suffix do
+          line_suffix(priority: COMMENT_PRIORITY) do
             text(" ")
             comment.format(self)
             break_parent
@@ -6231,7 +6234,7 @@ def format(q)
       q.group do
         q.format(beginning)
 
-        q.line_suffix do
+        q.line_suffix(priority: Formatter::HEREDOC_PRIORITY) do
           q.group do
             breakable.call
 

lib/syntax_tree/prettyprint.rb

@@ -213,9 +213,12 @@ def pretty_print(q)
   # constantly check where the line ends to avoid accidentally printing some
   # content after a line suffix node.
   class LineSuffix
-    attr_reader :contents
+    DEFAULT_PRIORITY = 1
 
-    def initialize(contents: [])
+    attr_reader :priority, :contents
+
+    def initialize(priority: DEFAULT_PRIORITY, contents: [])
+      @priority = priority
       @contents = contents
     end
 
@@ -741,10 +744,17 @@ def flush
 
     # This is a separate command stack that includes the same kind of triplets
     # as the commands variable. It is used to keep track of things that should
-    # go at the end of printed lines once the other doc nodes are
-    # accounted for. Typically this is used to implement comments.
+    # go at the end of printed lines once the other doc nodes are accounted for.
+    # Typically this is used to implement comments.
     line_suffixes = []
 
+    # This is a special sort used to order the line suffixes by both the
+    # priority set on the line suffix and the index it was in the original
+    # array.
+    line_suffix_sort = ->(line_suffix) {
+      [-line_suffix.last, -line_suffixes.index(line_suffix)]
+    }
+
     # This is a linear stack instead of a mutually recursive call defined on
     # the individual doc nodes for efficiency.
     while commands.any?
@@ -783,7 +793,7 @@ def flush
           commands << [indent, mode, doc.flat_contents] if doc.flat_contents
         end
       when LineSuffix
-        line_suffixes << [indent, mode, doc.contents]
+        line_suffixes << [indent, mode, doc.contents, doc.priority]
       when Breakable
         if mode == MODE_FLAT
           if doc.force?
@@ -804,7 +814,7 @@ def flush
         # to flush them now, as we are about to add a newline.
         if line_suffixes.any?
           commands << [indent, mode, doc]
-          commands += line_suffixes.reverse
+          commands += line_suffixes.sort_by(&line_suffix_sort)
           line_suffixes = []
           next
         end
@@ -838,7 +848,7 @@ def flush
       end
 
       if commands.empty? && line_suffixes.any?
-        commands += line_suffixes.reverse
+        commands += line_suffixes.sort_by(&line_suffix_sort)
         line_suffixes = []
       end
     end
@@ -1012,8 +1022,8 @@ def indent
 
   # Inserts a LineSuffix node into the print tree. The contents of the node are
   # determined by the block.
-  def line_suffix
-    doc = LineSuffix.new
+  def line_suffix(priority: LineSuffix::DEFAULT_PRIORITY)
+    doc = LineSuffix.new(priority: priority)
     target << doc
 
     with_target(doc.contents) { yield }