compiler: produce errors in C "filepath:line:column:" format

compiler/scanner.v

@@ -332,7 +332,7 @@ fn (s mut Scanner) scan() ScanRes {
 		// TODO allow double quotes
 		// case QUOTE:
 		// return scan_res(.str, s.ident_string())
-	case `\``:
+	case `\``: // ` // apostrophe balance comment. do not remove
 		return scan_res(.chartoken, s.ident_char())
 	case `(`:
 		return scan_res(.lpar, '')
@@ -563,9 +563,26 @@ fn (s mut Scanner) scan() ScanRes {
 	return scan_res(.eof, '')
 }
 
+fn (s &Scanner) find_current_line_start_position() int {
+  mut linestart := s.pos
+  for {
+    if linestart <= 0 {break}
+    if s.text[linestart] == 10 || s.text[linestart] == 13 { break }
+    linestart--
+  }
+  return linestart
+}
+
 fn (s &Scanner) error(msg string) {
-	file := s.file_path.all_after('/')
+	fullpath := os.realpath( s.file_path )
-	println('$file:${s.line_nr + 1} $msg')
+	column := s.pos - s.find_current_line_start_position()
+	// The filepath:line:col: format is the default C compiler
+	// error output format. It allows editors and IDE's like
+	// emacs to quickly find the errors in the output
+	// and jump to their source with a keyboard shortcut.
+	// Using only the filename leads to inability of IDE/editors
+	// to find the source file, when it is in another folder.
+	println('${fullpath}:${s.line_nr + 1}:$column: $msg')
 	exit(1)
 }
 
@@ -655,7 +672,7 @@ fn (s mut Scanner) ident_char() string {
 			len++
 		}
 		double_slash := s.expect('\\\\', s.pos - 2)
-		if s.text[s.pos] == `\`` && (s.text[s.pos - 1] != slash || double_slash) {
+		if s.text[s.pos] == `\`` && (s.text[s.pos - 1] != slash || double_slash) { // ` // apostrophe balance comment. do not remove
 			if double_slash {
 				len++
 			}
@@ -754,7 +771,7 @@ fn (s mut Scanner) get_opening_bracket() int {
 		if s.text[pos] == `(` && !inside_string {
 			parentheses--
 		}
-		if s.text[pos] == `\'` && s.text[pos - 1] != `\\` && s.text[pos - 1] != `\`` {
+		if s.text[pos] == `\'` && s.text[pos - 1] != `\\` && s.text[pos - 1] != `\`` { // ` // apostrophe balance comment. do not remove
 			inside_string = !inside_string
 		}
 		if parentheses == 0 {

compiler/tests/repl/error.repl

@@ -1,3 +1,3 @@
 println(a)
 ===output===
-.vrepl.v:2 undefined: `a`
+.vrepl.v:2:9: undefined: `a`

compiler/tests/repl/error_nosave.repl

@@ -1,5 +1,5 @@
 a
 33
 ===output===
-.vrepl_temp.v:2 undefined: `a`
+.vrepl_temp.v:2:9: undefined: `a`
 33

compiler/tests/repl/repl_test.v

@@ -2,7 +2,7 @@ import os
 
 fn test_repl() {
 	test_files := os.walk_ext('.', '.repl')
-
+	wd := os.getwd() + '/'  
   for file in test_files {
     content := os.read_file(file) or {
       assert false
@@ -19,7 +19,7 @@ fn test_repl() {
       assert false
       break
     }
-    result := r.output.replace('>>> ', '').replace('>>>', '').replace('... ', '').all_after('Use Ctrl-C or `exit` to exit\n')
+    result := r.output.replace('>>> ', '').replace('>>>', '').replace('... ', '').all_after('Use Ctrl-C or `exit` to exit\n').replace( wd, '' )
     assert result == output
     if result != output {
       println(file)

vlib/os/os.v

@@ -739,6 +739,26 @@ pub fn getwd() string {
 	}
 }
 
+// Returns the full absolute path for fpath, with all relative ../../, symlinks and so on resolved.
+// See http://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html
+// Also https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
+//  and https://insanecoding.blogspot.com/2007/11/implementing-realpath-in-c.html
+// NB: this particular rabbit hole is *deep* ...
+pub fn realpath(fpath string) string {
+	mut fullpath := malloc( MAX_PATH )
+	mut res := 0
+	$if windows {
+		res = int( C._fullpath( fullpath, fpath.str, MAX_PATH ) )
+	}
+	$else{
+		res = int( C.realpath( fpath.str, fullpath ) )
+	}
+	if res != 0 {
+		return string(fullpath, strlen(fullpath))
+	}
+	return fpath
+}
+
 // walk_ext returns a recursive list of all file paths ending with `ext`. 
 pub fn walk_ext(path, ext string) []string {
 	if !os.is_dir(path) {