From d0deec3ef3a439374e77aad6fd90bc8f9c5bcc90 Mon Sep 17 00:00:00 2001
From: Earlopain <14981592+Earlopain@users.noreply.github.com>
Date: Sun, 12 Jan 2025 15:11:00 +0100
Subject: [PATCH] [ruby/prism] Fix parser translator tokens for comment-only
 file

In https://github.com/ruby/prism/pull/3393 I made a mistake.
When there is no previous token, it wraps around to -1. Oops

Additionally, if a comment has no newline then the offset should be kept as is

https://github.com/ruby/prism/commit/3c266f1de4
---
 lib/prism/translation/parser/lexer.rb   | 10 +++++-----
 test/prism/fixtures/comment_single.txt  |  1 +
 test/prism/snapshots/comment_single.txt | 17 +++++++++++++++++
 3 files changed, 23 insertions(+), 5 deletions(-)
 create mode 100644 test/prism/fixtures/comment_single.txt
 create mode 100644 test/prism/snapshots/comment_single.txt

diff --git a/lib/prism/translation/parser/lexer.rb b/lib/prism/translation/parser/lexer.rb
index 49fdd2aea8..550219fc48 100644
--- a/lib/prism/translation/parser/lexer.rb
+++ b/lib/prism/translation/parser/lexer.rb
@@ -281,14 +281,14 @@ module Prism
                 location = range(token.location.start_offset, lexed[index][0].location.end_offset)
                 index += 1
               else
-                value.chomp!
-                location = range(token.location.start_offset, token.location.end_offset - 1)
+                is_at_eol = value.chomp!.nil?
+                location = range(token.location.start_offset, token.location.end_offset + (is_at_eol ? 0 : -1))
 
-                prev_token = lexed[index - 2][0]
+                prev_token = lexed[index - 2][0] if index - 2 >= 0
                 next_token = lexed[index][0]
 
-                is_inline_comment = prev_token.location.start_line == token.location.start_line
-                if is_inline_comment && !COMMENT_CONTINUATION_TYPES.include?(next_token&.type)
+                is_inline_comment = prev_token&.location&.start_line == token.location.start_line
+                if is_inline_comment && !is_at_eol && !COMMENT_CONTINUATION_TYPES.include?(next_token&.type)
                   tokens << [:tCOMMENT, [value, location]]
 
                   nl_location = range(token.location.end_offset - 1, token.location.end_offset)
diff --git a/test/prism/fixtures/comment_single.txt b/test/prism/fixtures/comment_single.txt
new file mode 100644
index 0000000000..72037a6ea1
--- /dev/null
+++ b/test/prism/fixtures/comment_single.txt
@@ -0,0 +1 @@
+foo # Bar
\ No newline at end of file
diff --git a/test/prism/snapshots/comment_single.txt b/test/prism/snapshots/comment_single.txt
new file mode 100644
index 0000000000..3de3483075
--- /dev/null
+++ b/test/prism/snapshots/comment_single.txt
@@ -0,0 +1,17 @@
+@ ProgramNode (location: (1,0)-(1,3))
+├── flags: ∅
+├── locals: []
+└── statements:
+    @ StatementsNode (location: (1,0)-(1,3))
+    ├── flags: ∅
+    └── body: (length: 1)
+        └── @ CallNode (location: (1,0)-(1,3))
+            ├── flags: newline, variable_call, ignore_visibility
+            ├── receiver: ∅
+            ├── call_operator_loc: ∅
+            ├── name: :foo
+            ├── message_loc: (1,0)-(1,3) = "foo"
+            ├── opening_loc: ∅
+            ├── arguments: ∅
+            ├── closing_loc: ∅
+            └── block: ∅