fmt: keep comments after imports (#8483)

vlib/v/ast/ast.v

@@ -284,6 +284,7 @@ pub:
 	alias_pos token.Position
 pub mut:
 	syms     []ImportSymbol // the list of symbols in `import {symbol1, symbol2}`
+	comments []Comment
 }
 
 // import symbol,for import {symbol} syntax

vlib/v/fmt/comments.v

@@ -105,6 +105,34 @@ pub fn (mut f Fmt) comments_after_last_field(comments []ast.Comment) {
 	}
 }
 
+pub fn (mut f Fmt) import_comments(comments []ast.Comment, options CommentsOptions) {
+	if comments.len == 0 {
+		return
+	}
+	if options.inline {
+		mut i := 0
+		for i = f.out_imports.len - 1; i >= 0; i-- {
+			if !f.out_imports.buf[i].is_space() { // != `\n` {
+				break
+			}
+		}
+		f.out_imports.go_back(f.out_imports.len - i - 1)
+	}
+	for c in comments {
+		ctext := c.text.trim_left('\x01')
+		if ctext == '' {
+			continue
+		}
+		mut out_s := if options.inline { ' ' } else { '' }
+		out_s += '//'
+		if is_first_char_alphanumeric(ctext) {
+			out_s += ' '
+		}
+		out_s += ctext
+		f.out_imports.writeln(out_s)
+	}
+}
+
 fn is_first_char_alphanumeric(s string) bool {
 	return match s[0] {
 		`a`...`z`, `A`...`Z`, `0`...`9` { true }

vlib/v/fmt/fmt.v

@@ -22,7 +22,6 @@ pub mut:
 	table              &table.Table
 	out_imports        strings.Builder
 	out                strings.Builder
-	out_save           strings.Builder
 	indent             int
 	empty_line         bool
 	line_len           int
@@ -272,6 +271,7 @@ pub fn (mut f Fmt) imports(imports []ast.Import) {
 		}
 		already_imported[import_text] = true
 		f.out_imports.writeln(import_text)
+		f.import_comments(imp.comments, inline: true)
 		num_imports++
 	}
 	if num_imports > 0 {

vlib/v/fmt/tests/comment_after_import_expected.vv

@@ -1,6 +0,0 @@
-import semver
-
-// as semver
-
-fn main() {
-}

vlib/v/fmt/tests/comment_after_import_input.vv

@@ -1,4 +0,0 @@
-import semver// as semver
-
-fn main() {
-}

vlib/v/fmt/tests/comments_keep.vv

@@ -1,3 +1,5 @@
+import semver // as sv
+
 enum Abc {
 	a
 	b // after a value

vlib/v/fmt/tests/import_single_input.vv

@@ -1,5 +0,0 @@
-import os
-
-fn main() {
-	os.system('echo hi')
-}

vlib/v/parser/parser.v

@@ -1907,6 +1907,7 @@ fn (mut p Parser) import_stmt() ast.Import {
 			return import_node
 		}
 	}
+	import_node.comments = p.eat_line_end_comments()
 	p.imports[mod_alias] = mod_name
 	// if mod_name !in p.table.imports {
 	p.table.imports << mod_name