toml: easier scanner configuration (#12016)

vlib/toml/input/input.v

@@ -3,6 +3,8 @@
 // that can be found in the LICENSE file.
 module input
 
+import os
+
 // Config is used to configure input to the toml module.
 // Only one of the fields `text` and `file_path` is allowed to be set at time of configuration.
 pub struct Config {
@@ -11,6 +13,23 @@ pub:
 	file_path string // '/path/to/file.toml'
 }
 
+// auto_config returns an, automatic determined, input Config based on heuristics
+// found in `toml`
+pub fn auto_config(toml string) ?Config {
+	mut config := Config{}
+	if !toml.contains('\n') && os.is_file(toml) {
+		config = Config{
+			file_path: toml
+		}
+	} else {
+		config = Config{
+			text: toml
+		}
+	}
+	config.validate() ?
+	return config
+}
+
 // validate returns an optional error if more than one of the fields
 // in `Config` has a non-default value (empty string).
 pub fn (c Config) validate() ? {
@@ -22,3 +41,14 @@ pub fn (c Config) validate() ? {
 			' ${typeof(c).name} must either contain a valid `file_path` OR a non-empty `text` field')
 	}
 }
+
+pub fn (c Config) read_input() ?string {
+	mut text := c.text
+	if os.is_file(c.file_path) {
+		text = os.read_file(c.file_path) or {
+			return error(@MOD + '.' + @STRUCT + '.' + @FN +
+				' Could not read "$c.file_path": "$err.msg"')
+		}
+	}
+	return text
+}

vlib/toml/scanner/scanner.v

@@ -38,7 +38,7 @@ pub:
 	tokenize_formating bool // if true, generate tokens for `\n`, ` `, `\t`, `\r` etc.
 }
 
-// new_scanner returns a new heap allocated `Scanner` instance.
+// new_scanner returns a new *heap* allocated `Scanner` instance.
 pub fn new_scanner(config Config) ?&Scanner {
 	config.input.validate() ?
 	mut text := config.input.text
@@ -56,6 +56,17 @@ pub fn new_scanner(config Config) ?&Scanner {
 	return s
 }
 
+// returns a new *stack* allocated `Scanner` instance.
+pub fn new_simple(toml_input string) ?Scanner {
+	config := Config{
+		input: input.auto_config(toml_input) ?
+	}
+	return Scanner{
+		config: config
+		text: config.input.read_input() ?
+	}
+}
+
 // scan returns the next token from the input.
 [direct_array_access]
 pub fn (mut s Scanner) scan() ?token.Token {

vlib/toml/toml.v

@@ -3,7 +3,6 @@
 // that can be found in the LICENSE file.
 module toml
 
-import os
 import toml.ast
 import toml.util
 import toml.input
@@ -71,17 +70,7 @@ pub fn parse_text(text string) ?Doc {
 // parse automatically try to determine if the type of `toml` is a file or text.
 // For explicit parsing of input types see `parse_file` or `parse_text`.
 pub fn parse(toml string) ?Doc {
-	mut input_config := input.Config{}
-	if !toml.contains('\n') && os.is_file(toml) {
-		input_config = input.Config{
-			file_path: toml
-		}
-	} else {
-		input_config = input.Config{
-			text: toml
-		}
-	}
-
+	mut input_config := input.auto_config(toml) ?
 	scanner_config := scanner.Config{
 		input: input_config
 	}