fix(toml): fix empty inline table bug (#6587)

Co-authored-by: Yoshiya Hinosawa <[email protected]>

Author: timreichen

toml/_parser.ts

@@ -207,9 +207,39 @@ function or<T>(parsers: ParserComponent<T>[]): ParserComponent<T> {
   };
 }
 
+/** Join the parse results of the given parser into an array.
+ *
+ * If the parser fails at the first attempt, it will return an empty array.
+ */
 function join<T>(
   parser: ParserComponent<T>,
   separator: string,
+): ParserComponent<T[]> {
+  const Separator = character(separator);
+  return (scanner: Scanner): ParseResult<T[]> => {
+    const out: T[] = [];
+    const first = parser(scanner);
+    if (!first.ok) return success(out);
+    out.push(first.body);
+    while (!scanner.eof()) {
+      if (!Separator(scanner).ok) break;
+      const result = parser(scanner);
+      if (!result.ok) {
+        throw new SyntaxError(`Invalid token after "${separator}"`);
+      }
+      out.push(result.body);
+    }
+    return success(out);
+  };
+}
+
+/** Join the parse results of the given parser into an array.
+ *
+ * This requires the parser to succeed at least once.
+ */
+function join1<T>(
+  parser: ParserComponent<T>,
+  separator: string,
 ): ParserComponent<T[]> {
   const Separator = character(separator);
   return (scanner: Scanner): ParseResult<T[]> => {
@@ -522,7 +552,7 @@ export function symbols(scanner: Scanner): ParseResult<unknown> {
   return success(value);
 }
 
-export const dottedKey = join(or([bareKey, basicString, literalString]), ".");
+export const dottedKey = join1(or([bareKey, basicString, literalString]), ".");
 
 const BINARY_REGEXP = /0b[01]+(?:_[01]+)*\b/y;
 export function binary(scanner: Scanner): ParseResult<number | string> {
@@ -639,11 +669,7 @@ export function inlineTable(
     scanner.next(2);
     return success({});
   }
-  const pairs = surround(
-    "{",
-    join(pair, ","),
-    "}",
-  )(scanner);
+  const pairs = surround("{", join(pair, ","), "}")(scanner);
   if (!pairs.ok) return failure();
   let table = {};
   for (const pair of pairs.body) {

toml/parse_test.ts

@@ -1408,3 +1408,16 @@ Deno.test({
     );
   },
 });
+
+Deno.test({
+  name: "parse() handles empty inline table",
+  fn() {
+    const input = `[package.metadata.details]
+readme = { }`;
+    const expected = {
+      package: { metadata: { details: { readme: {} } } },
+    };
+    const actual = parse(input);
+    assertEquals(actual, expected);
+  },
+});