From a86bf3254aeea70112ae2e4a2570b19b832934ff Mon Sep 17 00:00:00 2001
From: Lukas Neubert <serkonda@protonmail.com>
Date: Sat, 20 Feb 2021 15:05:05 +0100
Subject: [PATCH] fmt: keep empty line between if statement and comment 
 (#8846)

---
 vlib/v/fmt/comments.v                 | 15 +++++++++++----
 vlib/v/fmt/fmt.v                      | 19 +++++++++++--------
 vlib/v/fmt/tests/comments_expected.vv | 14 ++++++++++++++
 vlib/v/fmt/tests/comments_input.vv    | 16 ++++++++++++++++
 vlib/v/fmt/tests/comments_keep.vv     | 15 ++++++++++++---
 5 files changed, 64 insertions(+), 15 deletions(-)

diff --git a/vlib/v/fmt/comments.v b/vlib/v/fmt/comments.v
index b57c715bf7..da77004df7 100644
--- a/vlib/v/fmt/comments.v
+++ b/vlib/v/fmt/comments.v
@@ -15,11 +15,13 @@ enum CommentsLevel {
 // - inline: single-line comments will be on the same line as the last statement
 // - iembed: a /* ... */ embedded comment; used in expressions; // comments the whole line
 // - level:  either .keep (don't indent), or .indent (increment indentation)
+// - prev_line: the line number of the previous token
 struct CommentsOptions {
-	has_nl bool = true
-	inline bool
-	level  CommentsLevel
-	iembed bool
+	has_nl    bool = true
+	inline    bool
+	level     CommentsLevel
+	iembed    bool
+	prev_line int = -1
 }
 
 pub fn (mut f Fmt) comment(node ast.Comment, options CommentsOptions) {
@@ -79,14 +81,19 @@ pub fn (mut f Fmt) comment(node ast.Comment, options CommentsOptions) {
 }
 
 pub fn (mut f Fmt) comments(comments []ast.Comment, options CommentsOptions) {
+	mut prev_line := options.prev_line
 	for i, c in comments {
 		if !f.out.last_n(1)[0].is_space() {
 			f.write(' ')
 		}
+		if options.prev_line > -1 && c.pos.line_nr > prev_line + 1 {
+			f.writeln('')
+		}
 		f.comment(c, options)
 		if !options.iembed && (i < comments.len - 1 || options.has_nl) {
 			f.writeln('')
 		}
+		prev_line = c.pos.last_line
 	}
 }
 
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index a368c789bc..362d9aaf55 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -102,7 +102,7 @@ pub fn (mut f Fmt) write(s string) {
 }
 
 pub fn (mut f Fmt) writeln(s string) {
-	if f.indent > 0 && f.empty_line {
+	if f.indent > 0 && f.empty_line && s.len > 0 {
 		f.write_indent()
 	}
 	f.out.writeln(s)
@@ -1657,10 +1657,10 @@ pub fn (mut f Fmt) wrap_infix(start_pos int, start_len int, ignore_paren bool) {
 
 pub fn (mut f Fmt) if_expr(node ast.IfExpr) {
 	dollar := if node.is_comptime { '$' } else { '' }
-	mut single_line := node.branches.len == 2 && node.has_else
+	mut is_ternary := node.branches.len == 2 && node.has_else
 		&& branch_is_single_line(node.branches[0]) && branch_is_single_line(node.branches[1])
 		&& (node.is_expr || f.is_assign || f.is_struct_init || f.single_line_fields)
-	f.single_line_if = single_line
+	f.single_line_if = is_ternary
 	start_pos := f.out.len
 	start_len := f.line_len
 	for {
@@ -1693,20 +1693,20 @@ pub fn (mut f Fmt) if_expr(node ast.IfExpr) {
 				}
 			}
 			f.write('{')
-			if single_line {
+			if is_ternary {
 				f.write(' ')
 			} else {
 				f.writeln('')
 			}
 			f.stmts(branch.stmts)
-			if single_line {
+			if is_ternary {
 				f.write(' ')
 			}
 		}
 		// When a single line if is really long, write it again as multiline,
 		// except it is part of an InfixExpr.
-		if single_line && f.line_len > fmt.max_len.last() && !f.buffering {
-			single_line = false
+		if is_ternary && f.line_len > fmt.max_len.last() && !f.buffering {
+			is_ternary = false
 			f.single_line_if = false
 			f.out.go_back_to(start_pos)
 			f.line_len = start_len
@@ -1719,7 +1719,10 @@ pub fn (mut f Fmt) if_expr(node ast.IfExpr) {
 	f.single_line_if = false
 	if node.post_comments.len > 0 {
 		f.writeln('')
-		f.comments(node.post_comments, has_nl: false)
+		f.comments(node.post_comments, 
+			has_nl: false
+			prev_line: node.branches.last().body_pos.last_line
+		)
 	}
 }
 
diff --git a/vlib/v/fmt/tests/comments_expected.vv b/vlib/v/fmt/tests/comments_expected.vv
index 692275012e..c046e1f7af 100644
--- a/vlib/v/fmt/tests/comments_expected.vv
+++ b/vlib/v/fmt/tests/comments_expected.vv
@@ -82,3 +82,17 @@ fn linebreaks_in_block_comments() {
 	eggs
 	*/
 }
+
+fn between_if_branches() {
+	if spam {
+	}
+	// remove the empty line above
+	else if eggs {
+	}
+
+	if spam2 {
+	}
+	// remove the empty line below
+	else {
+	}
+}
diff --git a/vlib/v/fmt/tests/comments_input.vv b/vlib/v/fmt/tests/comments_input.vv
index 3078f64587..1c752c2f61 100644
--- a/vlib/v/fmt/tests/comments_input.vv
+++ b/vlib/v/fmt/tests/comments_input.vv
@@ -65,3 +65,19 @@ fn linebreaks_in_block_comments() {
 	spaces make no difference there
 	eggs */
 }
+
+fn between_if_branches() {
+	if spam {
+	}
+
+	// remove the empty line above
+	else if eggs {
+	}
+
+	if spam2 {
+	}
+	// remove the empty line below
+
+	else {
+	}
+}
diff --git a/vlib/v/fmt/tests/comments_keep.vv b/vlib/v/fmt/tests/comments_keep.vv
index ac4fee3bde..b923ee34e7 100644
--- a/vlib/v/fmt/tests/comments_keep.vv
+++ b/vlib/v/fmt/tests/comments_keep.vv
@@ -20,9 +20,6 @@ fn main() {
 	u := User{
 		name: 'Peter'
 	}
-	if true {
-	}
-	// some comment after an if without else
 	n := sizeof(User)
 	// else
 	// else {
@@ -60,3 +57,15 @@ fn linebreaks_in_block_comments() {
 	no problem
 	*****/
 }
+
+fn ifs_comments_and_empty_lines() {
+	if true {
+	}
+	// some comment after an if without else
+	if false {
+	}
+
+	// this is parsed as post_comment of the if but does not really belong there
+	// thereore keep the empty line
+	something_else()
+}