toml: add pub fn (d Doc) value_opt(key string) ?Any { and some tests for toml.parse_dotted_key/1

vlib/toml/tests/key_test.v

@@ -2,11 +2,12 @@ import os
 import toml
 import toml.to
 
-fn test_keys() {
-	toml_file :=
-		os.real_path(os.join_path(os.dir(@FILE), 'testdata', os.file_name(@FILE).all_before_last('.'))) +
-		'.toml'
-	toml_doc := toml.parse_file(toml_file) or { panic(err) }
+fn path_by_extension(ext string) string {
+	return os.join_path(os.dir(@VEXE), 'vlib/toml/tests/testdata/key_test.$ext')
+}
+
+fn test_keys() ? {
+	toml_doc := toml.parse_file(path_by_extension('toml'))?
 
 	mut value := toml_doc.value('34-11')
 	assert value.int() == 23
@@ -18,10 +19,30 @@ fn test_keys() {
 	assert value.int() == 42
 
 	toml_json := to.json(toml_doc)
-	out_file :=
-		os.real_path(os.join_path(os.dir(@FILE), 'testdata', os.file_name(@FILE).all_before_last('.'))) +
-		'.out'
-	out_file_json := os.read_file(out_file) or { panic(err) }
+	out_file_json := os.read_file(path_by_extension('out'))?
 	println(toml_json)
 	assert toml_json == out_file_json
+	//
+	if x := toml_doc.value_opt('unknown key') {
+		assert false
+	} else {
+		assert err.msg() == 'no value for key'
+	}
+	if x := toml_doc.value_opt("'a") {
+		assert false
+	} else {
+		assert err.msg() == 'invalid dotted key'
+	}
+}
+
+fn test_parse_dotted_key() ? {
+	assert toml.parse_dotted_key('')? == []
+	assert toml.parse_dotted_key('abc')? == ['abc']
+	assert toml.parse_dotted_key('tube.test."test.test".h."i.j."."k"')? == ['tube', 'test',
+		'test.test', 'h', 'i.j.', 'k']
+	if x := toml.parse_dotted_key("'some unclosed string") {
+		assert false
+	} else {
+		assert err.msg().starts_with('parse_dotted_key: could not parse key, missing closing string delimiter')
+	}
 }