Add inline comment support

README.md

@@ -37,6 +37,12 @@ Returns an array of leading comments. Each comment must start with `#`.
 
 Extends [Psych::Nodes::Node](https://docs.ruby-lang.org/en/3.1/Psych/Nodes/Node.html).
 
+### `Psych::Nodes::Node#inline_comment` -> `String | nil`
+
+Returns the inline comment. Each comment must start with `#`.
+
+Extends [Psych::Nodes::Node](https://docs.ruby-lang.org/en/3.1/Psych/Nodes/Node.html).
+
 ### `Psych::Nodes::Node#trailing_comments` -> `Array<String>`
 
 Returns an array of leading comments. Each comment must start with `#`.

lib/psych/comments/emitter.rb

@@ -131,6 +131,10 @@ def emit(node)
           else
             print stringify_adjust_scalar(node, INDENT * @indent)
           end
+          if node.inline_comment
+            space!
+            emit_comment(node.inline_comment)
+          end
         when Psych::Nodes::Mapping
           set_flow(flow?(node)) do
             if @flow
@@ -161,6 +165,7 @@ def emit(node)
                     emit(value)
                   end
                 end
+                emit_comment(node.inline_comment, newline: false) if node.inline_comment
                 newline!
               end
             end
@@ -192,6 +197,7 @@ def emit(node)
                     emit(subnode)
                   end
                 end
+                emit_comment(node.inline_comment, newline: false) if node.inline_comment
                 newline!
               end
             end
@@ -236,12 +242,12 @@ def emit_lookahead_comments(node)
         @comment_lookahead.push(node)
       end
 
-      def emit_comment(comment)
+      def emit_comment(comment, newline: true)
         unless /\A#[^\r\n]*\z/.match?(comment)
           raise ArgumentError, "Invalid comment: #{comment.inspect}"
         end
         print comment
-        newline!
+        newline! if newline
       end
 
       def indented(&block)
@@ -267,6 +273,8 @@ def single_line?(node)
       end
 
       def flow?(node)
+        return false if node.inline_comment # inline comments cannot be in flow
+
         case node
         when Psych::Nodes::Scalar, Psych::Nodes::Alias
           true

lib/psych/comments/node_ext.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class Psych::Nodes::Node
+  attr_accessor :inline_comment
+
   def leading_comments
     @leading_comments ||= []
   end

lib/psych/comments/parsing.rb

@@ -19,6 +19,10 @@ def sublines(sl, sc, el, ec)
         end
       end
 
+      def line_remaining(l, sc)
+        sublines(l, sc, l, nil)
+      end
+
       def char_at(l, c)
         (@lines[l] || "")[c]
       end
@@ -46,7 +50,10 @@ def visit(node)
         case node
         when Psych::Nodes::Scalar, Psych::Nodes::Alias
           node.leading_comments.push(*read_comments(node.start_line, node.start_column))
-          @last = [node.end_line, node.end_column]
+          has_delim = char_at(node.end_line, node.end_column) == ":"
+          inline_comment = line_remaining(node.end_line, node.end_column + (has_delim ? 1 : 0)).match(/^\s*(#.*)?$/)
+          node.inline_comment = inline_comment[1] if inline_comment && inline_comment[1]
+          @last = [node.end_line, node.end_column + (inline_comment&.values_at(0)&.first&.length || 0)]
         when Psych::Nodes::Sequence, Psych::Nodes::Mapping
           has_delim = /[\[{]/.match?(char_at(node.start_line, node.start_column))
           has_bullet = node.is_a?(Psych::Nodes::Sequence) && !has_delim
@@ -58,6 +65,8 @@ def visit(node)
           end
           if has_delim
             target = node.children[-1] || node
+            inline_comment = line_remaining(node.end_line, node.end_column).match(/^\s*(#.*)?$/)
+            node.inline_comment = inline_comment[1] if inline_comment && inline_comment[1]
             target.trailing_comments.push(*read_comments(node.end_line, node.end_column))
           end
         when Psych::Nodes::Document

spec/emitter/example2-out.yml

@@ -1,6 +1,5 @@
 # foo
-- foo
-# foo2
+- foo # foo2
 # foo
 - foo
 - foo: bar

spec/emitter/example5-out.yml

@@ -3,8 +3,7 @@ foo:
   bar: baz
   bar2:
     # test
-    foo: foo
-    #testtest
+    foo: foo #testtest
     # test
     bar: bar
   bar3:

spec/parsing_spec.rb

@@ -21,11 +21,22 @@
     end
 
     it "attaches comments to a scalar" do
-      ast = Psych::Comments.parse("# foo\nbar" + <<~YAML)
+      ast = Psych::Comments.parse(<<~YAML)
         # foo
         bar
       YAML
       expect(ast.root.leading_comments).to eq(["# foo"])
+      expect(ast.root.inline_comment).to eq(nil)
+      expect(ast.root.trailing_comments).to eq([])
+    end
+
+    it "attaches inline comments to a scalar" do
+      ast = Psych::Comments.parse(<<~YAML)
+        bar # foo
+      YAML
+      expect(ast.root.leading_comments).to eq([])
+      expect(ast.root.inline_comment).to eq("# foo")
+      expect(ast.root.trailing_comments).to eq([])
     end
 
     it "attaches multiple comments to a scalar" do
@@ -37,7 +48,7 @@
       expect(ast.root.leading_comments).to eq(["# foo", "# bar"])
     end
 
-    it "attaches comments to a mapping key" do
+    it "attaches leading comments to a mapping key" do
       ast = Psych::Comments.parse(<<~YAML)
         # foo
         bar: baz
@@ -46,7 +57,26 @@
       expect(ast.root.children[0].leading_comments).to eq(["# foo"])
     end
 
-    it "attaches comments to a mapping value" do
+    it "attaches inline comments to a mapping key" do
+      ast = Psych::Comments.parse(<<~YAML)
+        bar: # foo
+          baz
+      YAML
+      expect(ast.root).to be_a(Psych::Nodes::Mapping)
+      expect(ast.root.children[0].inline_comment).to eq("# foo")
+      expect(ast.root.children[1].inline_comment).to eq(nil)
+    end
+
+    it "attaches inline comments to a mapping value" do
+      ast = Psych::Comments.parse(<<~YAML)
+        bar: baz # foo
+      YAML
+      expect(ast.root).to be_a(Psych::Nodes::Mapping)
+      expect(ast.root.children[0].inline_comment).to eq(nil)
+      expect(ast.root.children[1].inline_comment).to eq("# foo")
+    end
+
+    it "attaches leading comments to a mapping value" do
       ast = Psych::Comments.parse(<<~YAML)
         bar:
           # foo
@@ -64,38 +94,73 @@
           bar2
         # baz-a
         - # baz-b
-          foo3: bar3
+          foo3: bar3 # baz-c
       YAML
       expect(ast.root).to be_a(Psych::Nodes::Sequence)
       expect(ast.root.children[0].leading_comments).to eq(["# foo"])
       expect(ast.root.children[1].leading_comments).to eq(["# bar"])
       expect(ast.root.children[2].leading_comments).to eq(["# baz-a"])
+      expect(ast.root.children[2].children[1].inline_comment).to eq("# baz-c")
+    end
+
+    it "attaches inline comments to empty flow mapping/sequence" do
+      ast = Psych::Comments.parse(<<~YAML)
+        foo: {} # foo
+        bar: [] # bar
+      YAML
+
+      expect(ast.root).to be_a(Psych::Nodes::Mapping)
+      expect(ast.root.children[1].inline_comment).to eq("# foo")
+      expect(ast.root.children[3].inline_comment).to eq("# bar")
+    end
+
+    it "attaches inline comments only to flow mapping/sequence" do
+      ast = Psych::Comments.parse(<<~YAML)
+        foo: { key: "name", values: ["a", "b", "c"] } # foo
+        bar: [{ key: "name", values: ["a", "b", "c"]}] # bar
+        baz:
+        - { key: "name", values: ["a", "b", "c"] } # baz
+      YAML
+      expected_comments = {
+        ast.root.children[1] => "# foo",
+        ast.root.children[3] => "# bar",
+        ast.root.children[5].children[0] => "# baz"
+      }
+      visit = lambda do |node|
+        expect(node.inline_comment).to eq(expected_comments[node])
+        node.children&.each { |child| visit.call(child) }
+      end
+      visit.call(ast.root)
     end
 
     it "attaches comments to flow mapping" do
       ast = Psych::Comments.parse(<<~YAML)
-        # foo
+        # leading
         {
-          foo: bar
+          foo: bar # foo
           # bar
-        }
+        } # inline
       YAML
       expect(ast.root).to be_a(Psych::Nodes::Mapping)
-      expect(ast.root.leading_comments).to eq(["# foo"])
+      expect(ast.root.leading_comments).to eq(["# leading"])
+      expect(ast.root.inline_comment).to eq("# inline")
+      expect(ast.root.children[1].inline_comment).to eq("# foo")
       expect(ast.root.children[1].trailing_comments).to eq(["# bar"])
     end
 
     it "attaches comments to flow sequence" do
       ast = Psych::Comments.parse(<<~YAML)
         # foo
         [
-          foo
-          # bar
-        ]
+          foo # bar
+          # baz
+        ] # bazza
       YAML
       expect(ast.root).to be_a(Psych::Nodes::Sequence)
       expect(ast.root.leading_comments).to eq(["# foo"])
-      expect(ast.root.children[0].trailing_comments).to eq(["# bar"])
+      expect(ast.root.inline_comment).to eq("# bazza")
+      expect(ast.root.children[0].inline_comment).to eq("# bar")
+      expect(ast.root.children[0].trailing_comments).to eq(["# baz"])
     end
 
     it "attaches comments to document" do