vfmt: add ability to use vfmt as a filter from stdin to stdout (#8432)

cmd/tools/vfmt.v

@@ -29,17 +29,6 @@ struct FormatOptions {
 
 const (
 	formatted_file_token = '\@\@\@' + 'FORMATTED_FILE: '
-	platform_and_file_extensions = [
-		['windows', '_windows.v'],
-		['linux', '_lin.v', '_linux.v', '_nix.v'],
-		['macos', '_mac.v', '_darwin.v'],
-		['freebsd', '_bsd.v', '_freebsd.v'],
-		['netbsd', '_bsd.v', '_netbsd.v'],
-		['openbsd', '_bsd.v', '_openbsd.v'],
-		['solaris', '_solaris.v'],
-		['haiku', '_haiku.v'],
-		['qnx', '_qnx.v'],
-	]
 	vtmp_folder          = util.get_vtmp_folder()
 )
 
@@ -100,7 +89,11 @@ fn main() {
 		}
 		files << file
 	}
-	if files.len == 0 {
+	if is_atty(0) == 0 && files.len == 0 {
+		foptions.format_pipe()
+		exit(0)
+	}
+	if files.len == 0 || '-help' in args || '--help' in args {
 		vhelp.show_topic('fmt')
 		exit(0)
 	}
@@ -183,6 +176,26 @@ fn (foptions &FormatOptions) format_file(file string) {
 	eprintln('$formatted_file_token$vfmt_output_path')
 }
 
+fn (foptions &FormatOptions) format_pipe() {
+	mut prefs := pref.new_preferences()
+	prefs.is_fmt = true
+	if foptions.is_verbose {
+		eprintln('vfmt2 running fmt.fmt over stdin')
+	}
+	input_text := os.get_raw_lines_joined()
+	table := table.new_table()
+	// checker := checker.new_checker(table, prefs)
+	file_ast := parser.parse_text(input_text, '', table, .parse_comments, prefs, &ast.Scope{
+		parent: 0
+	})
+	// checker.check(file_ast)
+	formatted_content := fmt.fmt(file_ast, table, foptions.is_debug)
+	print(formatted_content)
+	if foptions.is_verbose {
+		eprintln('fmt.fmt worked and $formatted_content.len bytes were written to stdout.')
+	}
+}
+
 fn print_compiler_options(compiler_params &pref.Preferences) {
 	eprintln('         os: ' + compiler_params.os.str())
 	eprintln('  ccompiler: $compiler_params.ccompiler')
@@ -264,17 +277,6 @@ fn (f FormatOptions) str() string {
 		' is_verify: $f.is_verify" }'
 }
 
-fn file_to_target_os(file string) string {
-	for extensions in platform_and_file_extensions {
-		for ext in extensions {
-			if file.ends_with(ext) {
-				return extensions[0]
-			}
-		}
-	}
-	return ''
-}
-
 fn file_to_mod_name_and_is_module_file(file string) (string, bool) {
 	mut mod_name := 'main'
 	mut is_module_file := false

cmd/v/help/fmt.txt

@@ -1,6 +1,8 @@
 Usage:
   v fmt [options] path_to_source.v [path_to_other_source.v]
   v fmt [options] path/to/dir [path/to/other_dir]
+  cat source.v | v fmt
+        Read source code from stdin, output formatted file to stdout.
 
 Formats the given V source files or recursively formats all files in the directory,
 then prints their formatted source to stdout.

vlib/os/os.v

@@ -265,6 +265,25 @@ pub fn get_lines_joined() string {
 	return inputstr
 }
 
+// get_raw_lines_joined reads *all* input lines from stdin.
+// It returns them as one large string. NB: unlike os.get_lines_joined,
+// empty lines (that contain only `\r\n` or `\n`), will be present in
+// the output.
+// Reading is stopped, only on EOF of stdin.
+pub fn get_raw_lines_joined() string {
+	mut line := ''
+	mut lines := []string{}
+	for {
+		line = get_raw_line()
+		if line.len <= 0 {
+			break
+		}
+		lines << line
+	}
+	res := lines.join('')
+	return res
+}
+
 // user_os returns current user operating system name.
 pub fn user_os() string {
 	$if linux {

vlib/v/pref/pref.v

@@ -457,15 +457,7 @@ pub fn parse_args(args []string) (&Preferences, string) {
 				output_option = '-o "$tmp_exe_file_path"'
 			}
 			tmp_v_file_path := '${tmp_file_path}.v'
-			mut lines := []string{}
+			contents := os.get_raw_lines_joined()
-			for {
-				iline := os.get_raw_line()
-				if iline.len == 0 {
-					break
-				}
-				lines << iline
-			}
-			contents := lines.join('')
 			os.write_file(tmp_v_file_path, contents) or {
 				panic('Failed to create temporary file $tmp_v_file_path')
 			}