scanner: add support for @VMOD_FILE

doc/docs.md

@@ -1622,6 +1622,32 @@ $if debug {
 If you want an `if` to be evaluated at compile time it must be prefixed with a `$` sign. Right now it can only be used to detect
 an OS or a `-debug` compilation option.
 
+## Compile time pseudo variables
+
+V also gives your code access to a set of pseudo string variables, that are substituted at compile time:
+
+- `@FN` => replaced with the name of the current V function
+- `@MOD` => replaced with the name of the current V module
+- `@STRUCT` => replaced with the name of the current V struct
+- `@FILE` => replaced with the path of the V source file
+- `@LINE` => replaced with the V line number where it appears (as a string).
+- `@COLUMN` => replaced with the column where it appears (as a string).
+- `@VEXE` => replaced with the path to the V compiler
+- `@VHASH`  => replaced with the shortened commit hash of the V compiler (as a string).
+- `@VMOD_FILE` => replaced with the contents of the nearest v.mod file (as a string).
+
+That allows you to do the following example, useful while debugging/logging/tracing your code:
+```v
+eprintln( 'file: ' + @FILE + ' | line: ' + @LINE + ' | fn: ' + @MOD + '.' + @FN)
+```
+
+Another example, is if you want to embed the version/name from v.mod *inside* your executable:
+```v
+import v.vmod
+vm := vmod.decode( @VMOD_FILE ) or { panic(err) }
+eprintln('$vm.name $vm.version\n $vm.description')
+```
+
 ## Reflection via codegen
 
 Having built-in JSON support is nice, but V also allows you to create efficient

vlib/v/scanner/scanner.v

@@ -7,6 +7,7 @@ import os
 import v.token
 import v.pref
 import v.util
+import v.vmod
 
 const (
 	single_quote = `\'`
@@ -32,6 +33,7 @@ pub mut:
 	fn_name                     string // needed for @FN
 	mod_name                    string // needed for @MOD
 	struct_name                 string // needed for @STRUCT
+	vmod_file_content           string // needed for @VMOD_FILE, contents of the file, *NOT its path*
 	is_print_line_on_error      bool
 	is_print_colored_error      bool
 	is_print_rel_paths_on_error bool
@@ -745,6 +747,7 @@ pub fn (mut s Scanner) scan() token.Token {
 			// @LINE => will be substituted with the V line number where it appears (as a string).
 			// @COLUMN => will be substituted with the column where it appears (as a string).
 			// @VHASH  => will be substituted with the shortened commit hash of the V compiler (as a string).
+			// @VMOD_FILE => will be substituted with the contents of the nearest v.mod file (as a string).
 			// This allows things like this:
 			// println( 'file: ' + @FILE + ' | line: ' + @LINE + ' | fn: ' + @MOD + '.' + @FN)
 			// ... which is useful while debugging/tracing
@@ -773,6 +776,17 @@ pub fn (mut s Scanner) scan() token.Token {
 			if name == 'VHASH' {
 				return s.new_token(.string, util.vhash(), 6)
 			}
+			if name == 'VMOD_FILE' {
+				if s.vmod_file_content.len == 0 {
+					vmod_file_location := vmod.mod_file_cacher.get( os.dir( os.real_path(s.file_path) ) )
+					if vmod_file_location.vmod_file.len == 0 {
+						s.error('@VMOD_FILE can be used only in projects, that have v.mod file')
+					}
+					vmod_content := os.read_file(vmod_file_location.vmod_file) or {''}
+					s.vmod_file_content = vmod_content
+				}
+				return s.new_token(.string, s.vmod_file_content, 10)
+			}
 			if !token.is_key(name) {
 				s.error('@ must be used before keywords (e.g. `@type string`)')
 			}

vlib/v/scanner/scanner_test.v

@@ -82,3 +82,12 @@ fn test_scan() {
 
 
 }
+
+fn test_vmod_file() {
+	content := @VMOD_FILE
+	assert content.len > 0
+	assert content.contains('Module {')
+	assert content.contains('name:')
+	assert content.contains('version:')
+	assert content.contains('description:')
+}