keep indent state in fmt Buf

compiler/fmt/src/spaces.rs

@@ -1,6 +1,8 @@
 use bumpalo::collections::String;
 use roc_parse::ast::CommentOrNewline;
 
+use crate::Buf;
+
 /// The number of spaces to indent.
 pub const INDENT: u16 = 4;
 
@@ -17,7 +19,7 @@ pub fn add_spaces(buf: &mut String<'_>, spaces: u16) {
 }
 
 pub fn fmt_default_spaces<'a>(
-    buf: &mut String<'a>,
+    buf: &mut Buf<'a>,
     spaces: &[CommentOrNewline<'a>],
     default: &str,
     indent: u16,
@@ -29,7 +31,7 @@ pub fn fmt_default_spaces<'a>(
     }
 }
 
-pub fn fmt_spaces<'a, 'b, I>(buf: &mut String<'a>, spaces: I, indent: u16)
+pub fn fmt_spaces<'a, 'b, I>(buf: &mut Buf<'a>, spaces: I, indent: u16)
 where
     I: Iterator<Item = &'b CommentOrNewline<'b>>,
 {
@@ -38,19 +40,14 @@ where
     // Only ever print two newlines back to back.
     // (Two newlines renders as one blank line.)
     let mut consecutive_newlines = 0;
-    let mut iter = spaces.peekable();
 
     let mut encountered_comment = false;
 
-    while let Some(space) = iter.next() {
+    for space in spaces {
         match space {
             Newline => {
                 if !encountered_comment && (consecutive_newlines < 2) {
-                    if iter.peek() == Some(&&Newline) && consecutive_newlines < 1 {
-                        buf.push('\n');
-                    } else {
-                        newline(buf, indent);
-                    }
+                    buf.newline();
 
                     // Don't bother incrementing it if we're already over the limit.
                     // There's no upside, and it might eventually overflow,
@@ -58,14 +55,16 @@ where
                 }
             }
             LineComment(comment) => {
+                buf.indent(indent);
                 fmt_comment(buf, comment);
-                newline(buf, indent);
+                buf.newline();
 
                 encountered_comment = true;
             }
             DocComment(docs) => {
+                buf.indent(indent);
                 fmt_docs(buf, docs);
-                newline(buf, indent);
+                buf.newline();
 
                 encountered_comment = true;
             }
@@ -86,7 +85,7 @@ pub enum NewlineAt {
 /// at the beginning or at the end of the block
 /// in the case of there is some comment in the `spaces` argument.
 pub fn fmt_comments_only<'a, 'b, I>(
-    buf: &mut String<'a>,
+    buf: &mut Buf<'a>,
     spaces: I,
     new_line_at: NewlineAt,
     indent: u16,
@@ -103,26 +102,28 @@ pub fn fmt_comments_only<'a, 'b, I>(
             Newline => {}
             LineComment(comment) => {
                 if comment_seen || new_line_at == Top || new_line_at == Both {
-                    newline(buf, indent);
+                    buf.newline();
                 }
+                buf.indent(indent);
                 fmt_comment(buf, comment);
                 comment_seen = true;
             }
             DocComment(docs) => {
                 if comment_seen || new_line_at == Top || new_line_at == Both {
-                    newline(buf, indent);
+                    buf.newline();
                 }
+                buf.indent(indent);
                 fmt_docs(buf, docs);
                 comment_seen = true;
             }
         }
     }
     if comment_seen && (new_line_at == Bottom || new_line_at == Both) {
-        newline(buf, indent);
+        buf.newline();
     }
 }
 
-fn fmt_comment<'a>(buf: &mut String<'a>, comment: &str) {
+fn fmt_comment<'a>(buf: &mut Buf<'a>, comment: &str) {
     buf.push('#');
     if !comment.starts_with(' ') {
         buf.push(' ');
@@ -130,7 +131,7 @@ fn fmt_comment<'a>(buf: &mut String<'a>, comment: &str) {
     buf.push_str(comment);
 }
 
-fn fmt_docs<'a>(buf: &mut String<'a>, docs: &str) {
+fn fmt_docs<'a>(buf: &mut Buf<'a>, docs: &str) {
     buf.push_str("##");
     if !docs.starts_with(' ') {
         buf.push(' ');