From f3dd9e411f4485fcdc37bc89c16cd8c2f8817a4c Mon Sep 17 00:00:00 2001
From: Joshua Warner <joshuawarner32@gmail.com>
Date: Sun, 5 Dec 2021 12:18:00 -0800
Subject: [PATCH] Keep trailing comments at the end of a file

---
 compiler/fmt/tests/test_fmt.rs   | 37 +++++++++++++++++++++-----------
 compiler/parse/src/blankspace.rs | 10 +++++++++
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/compiler/fmt/tests/test_fmt.rs b/compiler/fmt/tests/test_fmt.rs
index 6adbed8ee3..89d864caff 100644
--- a/compiler/fmt/tests/test_fmt.rs
+++ b/compiler/fmt/tests/test_fmt.rs
@@ -5,7 +5,6 @@ extern crate roc_fmt;
 
 #[cfg(test)]
 mod test_fmt {
-    use bumpalo::collections::String;
     use bumpalo::Bump;
     use roc_fmt::annotation::{Formattable, Newlines, Parens};
     use roc_fmt::def::fmt_def;
@@ -49,7 +48,6 @@ mod test_fmt {
     fn module_formats_to(src: &str, expected: &str) {
         let arena = Bump::new();
         let src = src.trim_end();
-        let expected = expected.trim_end();
 
         match module::parse_header(&arena, State::new(src.as_bytes())) {
             Ok((actual, state)) => {
@@ -2571,19 +2569,35 @@ mod test_fmt {
     fn single_line_interface() {
         module_formats_same(indoc!(
             r#"
-                interface Foo exposes [] imports []
-            "#
+                interface Foo exposes [] imports []"#
         ));
     }
 
+    #[test]
+    fn defs_with_trailing_comment() {
+        // TODO: make the formatter add a space between '42' and # below:
+        module_formats_to(
+            indoc!(
+                r#"
+            interface Foo exposes [] imports []
+            a = 42 # Yay greetings"#
+            ),
+            indoc!(
+                r#"
+            interface Foo exposes [] imports []
+            a = 42# Yay greetings
+            "#
+            ),
+        );
+    }
+
     #[test]
     fn multiline_interface() {
         module_formats_same(indoc!(
             r#"
                 interface Foo
                     exposes []
-                    imports []
-            "#
+                    imports []"#
         ));
     }
 
@@ -2593,8 +2607,7 @@ mod test_fmt {
             r#"
                 interface Foo
                     exposes [ Bar, Baz, a, b ]
-                    imports []
-            "#
+                    imports []"#
         ));
     }
 
@@ -2604,8 +2617,7 @@ mod test_fmt {
             r#"
                 interface Foo
                     exposes [ Bar, Baz, a, b ]
-                    imports [ Blah, Thing.{ foo, bar }, Stuff ]
-            "#
+                    imports [ Blah, Thing.{ foo, bar }, Stuff ]"#
         ));
     }
 
@@ -2613,8 +2625,7 @@ mod test_fmt {
     fn single_line_app() {
         module_formats_same(indoc!(
             r#"
-                app "Foo" packages { base: "platform" } imports [] provides [ main ] to base
-            "#
+                app "Foo" packages { base: "platform" } imports [] provides [ main ] to base"#
         ));
     }
 
@@ -2638,7 +2649,7 @@ mod test_fmt {
                 putLine :Str -> Effect {}, \
                 putInt :I64 -> Effect {}, \
                 getInt :Effect { value : I64, errorCode : [ A, B ], isError : Bool } \
-            } ",
+            }",
         );
     }
 
diff --git a/compiler/parse/src/blankspace.rs b/compiler/parse/src/blankspace.rs
index ff10152e84..f2b753b914 100644
--- a/compiler/parse/src/blankspace.rs
+++ b/compiler/parse/src/blankspace.rs
@@ -363,6 +363,16 @@ fn eat_line_comment<'a>(
         }
     }
 
+    // We made it to the end of the bytes. This means there's a comment without a trailing newline.
+    let delta = (col - initial_col) as usize;
+    let comment = unsafe { std::str::from_utf8_unchecked(&initial[..delta]) };
+
+    if is_doc_comment {
+        comments_and_newlines.push(CommentOrNewline::DocComment(comment));
+    } else {
+        comments_and_newlines.push(CommentOrNewline::LineComment(comment));
+    }
+
     Good {
         row,
         col,