fmt: initial support for -debug

cmd/tools/vfmt.v

@@ -152,7 +152,7 @@ fn (foptions &FormatOptions) format_file(file string) {
 		parent: 0
 	})
 	// checker.check(file_ast)
-	formatted_content := fmt.fmt(file_ast, table)
+	formatted_content := fmt.fmt(file_ast, table, foptions.is_debug)
 	file_name := os.file_name(file)
 	vfmt_output_path := os.join_path(os.temp_dir(), 'vfmt_' + file_name)
 	os.write_file(vfmt_output_path, formatted_content)

cmd/v/help/fmt.txt

@@ -9,7 +9,9 @@ Options:
   -diff Display only diffs between the formatted source and the original source.
   -l    List files whose formatting differs from vfmt.
   -w    Write result to (source) file(s) instead of to stdout.
-  -2    Use the new V parser/vfmt. NB: this is EXPERIMENTAL for now.
-          The new vfmt is much faster and more forgiving.
-          It also may EAT some of your code for now.
-          Please be careful, and make frequent BACKUPS, when running with -vfmt2 .
+ -debug Print the kinds of encountered AST statements/expressions on stderr.
+
+NB: vfmt after 2020/04/01 is based on the new AST compiler code, and
+thus is much faster, and more flexible than before.
+It may also EAT some of your code for now, so please be careful, and
+make frequent BACKUPS.

vlib/v/fmt/fmt.v

@@ -28,15 +28,17 @@ mut:
 	auto_imports   []string // automatically inserted imports that the user forgot to specify
 	import_pos     int // position of the imports in the resulting string for later autoimports insertion
 	used_imports   []string // to remove unused imports
+	is_debug       bool
 }
 
-pub fn fmt(file ast.File, table &table.Table) string {
+pub fn fmt(file ast.File, table &table.Table, is_debug bool) string {
 	mut f := Fmt{
 		out: strings.new_builder(1000)
 		out_imports: strings.new_builder(200)
 		table: table
 		indent: 0
 		file: file
+		is_debug: is_debug
 	}
 	f.cur_mod = 'main'
 	for stmt in file.stmts {
@@ -141,6 +143,9 @@ fn (mut f Fmt) stmts(stmts []ast.Stmt) {
 }
 
 fn (mut f Fmt) stmt(node ast.Stmt) {
+	if f.is_debug {
+		eprintln('stmt: ${node.position():-42} | node: ${typeof(node):-20}')
+	}
 	match node {
 		ast.AssignStmt {
 			for i, ident in it.left {
@@ -492,6 +497,9 @@ fn (f &Fmt) type_to_str(t table.Type) string {
 }
 
 fn (mut f Fmt) expr(node ast.Expr) {
+	if f.is_debug {
+		eprintln('expr: ${node.position():-42} | node: ${typeof(node):-20} | ${node.str()}')
+	}
 	match node {
 		ast.AnonFn {
 			f.fn_decl(it.decl)

vlib/v/fmt/fmt_keep_test.v

@@ -45,7 +45,7 @@ fn test_fmt() {
 		file_ast := parser.parse_file(ipath, table, .parse_comments, &pref.Preferences{}, &ast.Scope{
 			parent: 0
 		})
-		result_ocontent := fmt.fmt(file_ast, table)
+		result_ocontent := fmt.fmt(file_ast, table, false)
 		if expected_ocontent != result_ocontent {
 			fmt_bench.fail()
 			eprintln(fmt_bench.step_message_fail('file ${ipath} after formatting, does not look as expected.'))

vlib/v/fmt/fmt_test.v

@@ -47,7 +47,7 @@ fn test_fmt() {
 		file_ast := parser.parse_file(ipath, table, .parse_comments, &pref.Preferences{}, &ast.Scope{
 			parent: 0
 		})
-		result_ocontent := fmt.fmt(file_ast, table)
+		result_ocontent := fmt.fmt(file_ast, table, false)
 		if expected_ocontent != result_ocontent {
 			fmt_bench.fail()
 			eprintln(fmt_bench.step_message_fail('file ${ipath} after formatting, does not look as expected.'))