toml: support empty tables (#12504)

vlib/toml/parser/parser.v

@@ -254,10 +254,7 @@ fn (p Parser) check_explicitly_declared(key DottedKey) ? {
 // See also `find_in_table`.
 pub fn (mut p Parser) find_table() ?&map[string]ast.Value {
 	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'locating "$p.root_map_key" in map ${ptr_str(p.root_map)}')
-	mut t := &map[string]ast.Value{}
+	mut t := unsafe { &p.root_map }
-	unsafe {
-		t = &p.root_map
-	}
 	if p.root_map_key.len == 0 {
 		return t
 	}
@@ -265,6 +262,16 @@ pub fn (mut p Parser) find_table() ?&map[string]ast.Value {
 	return p.find_in_table(mut t, p.root_map_key)
 }
 
+// allocate_table allocates all tables in "dotted" `key` (`a.b.c`) in the *root* table.
+pub fn (mut p Parser) allocate_table(key DottedKey) ? {
+	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'allocating "$key" in map ${ptr_str(p.root_map)}')
+	mut t := unsafe { &p.root_map }
+	if key.len == 0 {
+		return
+	}
+	p.allocate_in_table(mut t, key) ?
+}
+
 // sub_table_key returns the logic parts of a dotted key (`a.b.c`) for
 // use with the `find_sub_table` method.
 pub fn (mut p Parser) sub_table_key(key DottedKey) (DottedKey, DottedKey) {
@@ -286,10 +293,7 @@ pub fn (mut p Parser) find_sub_table(key DottedKey) ?&map[string]ast.Value {
 		ky = key
 	}
 	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'locating "$ky" in map ${ptr_str(p.root_map)}')
-	mut t := &map[string]ast.Value{}
+	mut t := unsafe { &p.root_map }
-	unsafe {
-		t = &p.root_map
-	}
 	if ky.len == 0 {
 		return t
 	}
@@ -306,10 +310,7 @@ pub fn (mut p Parser) find_in_table(mut table map[string]ast.Value, key DottedKe
 	// I'm still not quite sure *exactly* why it works. All I can leave here is a hope
 	// that this kind of minefield someday will be easier in V :)
 	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'locating "$key" in map ${ptr_str(table)}')
-	mut t := &map[string]ast.Value{}
+	mut t := unsafe { &table }
-	unsafe {
-		t = &table
-	}
 	unsafe {
 		for k in key {
 			if val := t[k] {
@@ -332,6 +333,30 @@ pub fn (mut p Parser) find_in_table(mut table map[string]ast.Value, key DottedKe
 	return t
 }
 
+// allocate_in_table allocates all tables in "dotted" `key` (`a.b.c`) in `table`.
+pub fn (mut p Parser) allocate_in_table(mut table map[string]ast.Value, key DottedKey) ? {
+	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'allocating "$key" in map ${ptr_str(table)}')
+	mut t := unsafe { &table }
+	unsafe {
+		for k in key {
+			if val := t[k] {
+				util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'found key "$k" in $t.keys()')
+				if val is map[string]ast.Value {
+					t = &(val as map[string]ast.Value)
+				} else {
+					return error(@MOD + '.' + @STRUCT + '.' + @FN +
+						' "$k" in "$key" is not a map ($val.type_name())')
+				}
+			} else {
+				util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'no key "$k" in "$key" found, allocating new map at key "$k" in map ${ptr_str(t)}"')
+				t[k] = map[string]ast.Value{}
+				t = &(t[k] as map[string]ast.Value)
+				util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'allocated new map ${ptr_str(t)}"')
+			}
+		}
+	}
+}
+
 // dotted_key returns a string of the next tokens parsed as
 // sub/nested/path keys (e.g. `a.b.c`). In TOML, this form of key is referred to as a "dotted" key.
 pub fn (mut p Parser) dotted_key() ?DottedKey {
@@ -476,6 +501,7 @@ pub fn (mut p Parser) root_table() ? {
 					p.ignore_while(parser.space_formatting)
 					util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'setting root map key to `$dotted_key` at "$p.tok.kind" "$p.tok.lit"')
 					p.root_map_key = dotted_key
+					p.allocate_table(p.root_map_key) ?
 					p.expect(.rsbr) ?
 					p.peek_for_correct_line_ending_or_fail() ?
 				} else {
@@ -497,6 +523,7 @@ pub fn (mut p Parser) root_table() ? {
 
 					util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'setting root map key to `$dotted_key` at "$p.tok.kind" "$p.tok.lit"')
 					p.root_map_key = dotted_key
+					p.allocate_table(p.root_map_key) ?
 					p.next() ?
 					p.expect(.rsbr) ?
 					p.peek_for_correct_line_ending_or_fail() ?
@@ -822,10 +849,7 @@ pub fn (mut p Parser) double_array_of_tables_contents(target_key DottedKey) ?[]a
 				} else {
 					key, val := p.key_value() ?
 
-					mut t := &map[string]ast.Value{}
+					mut t := unsafe { &tbl }
-					unsafe {
-						t = &tbl
-					}
 					if implicit_allocation_key.len > 0 {
 						t = p.find_in_table(mut tbl, implicit_allocation_key) ?
 					}

vlib/toml/tests/burntsushi.toml-test_test.v

@@ -31,18 +31,8 @@ const (
 		// Comment
 		'comment/tricky.toml',
 		// Table
-		'table/empty.toml',
 		'table/array-implicit.toml',
-		'table/sub-empty.toml',
-		'table/without-super.toml',
-		'table/whitespace.toml',
 		'table/names.toml',
-		'table/no-eol.toml',
-		'table/keyword.toml',
-		// Array
-		'array/string-quote-comma.toml',
-		'array/string-quote-comma-2.toml',
-		'array/table-array-string-backslash.toml',
 		// Date-time
 		'datetime/milliseconds.toml',
 		// Inline-table