feat(parse): permit number and bigint underscore separators

Author: michaelfig

packages/parse/src/quasi-json.js

@@ -116,15 +116,16 @@ hex <- digit / [a-fA-F];
 
 NUMBER <- < int frac? exp? > _WSN;
 
-int <- [1-9] digit+
+int <- [1-9] digits
 / digit
-/ MINUS digit
-/ MINUS [1-9] digit+;
+/ MINUS [1-9] digits
+/ MINUS digit;
 
 digit <- [0-9];
+digits <- digit*;
 
-frac <- '.' digit+;
-exp <- [Ee] [+\-]? digit+;
+frac <- '.' digits;
+exp <- [Ee] [+\-]? digits;
 
 # _WSN is whitespace or a non-ident character.
 _WSN <- ~[$A-Za-z_] _WS    ${_ => SKIP};

packages/parse/src/quasi-justin.js

@@ -10,6 +10,7 @@
 //   * undefined.
 //   * includes all floating point values: NaN, Infinity, -Infinity
 //   * includes BigInt literals: 123n
+//   * numbers and bigints can have optional underscores: 1_000_000n
 
 // Justin also includes most pure JavaScript expressions. Justin does not
 // include function expressions or variable or function
@@ -82,8 +83,15 @@ const makeJustin = peg => {
     RIGHT_PAREN <- ")" _WS;
     STARSTAR <- "**" _WS;
 
+    # Allow optional underscore digit separators.
+    digits <- super.digit ** ("_"?);
+    NUMBER <- super.NUMBER ${ns => ns.replaceAll('_', '')};
+
     # BigInts are not supported in JSON, but they are in Justin.
-    bigintLiteral <- < int > "n" _WSN ${int => ['data', BigInt(int)]};
+    bigintLiteral <- < int > "n" _WSN ${ns => [
+      'data',
+      BigInt(ns.replaceAll('_', '')),
+    ]};
 
     # Define Javascript-style comments.
     _WS <- super._WS (EOL_COMMENT / MULTILINE_COMMENT)?   ${_ => SKIP};

packages/parse/test/test-justin.js

@@ -10,6 +10,9 @@ test('data', t => {
     t.assert(val, message),
   );
   t.deepEqual(parse(`12345`), ast(0, 'data', 12345));
+  t.deepEqual(parse(`12_345`), ast(0, 'data', 12345));
+  t.deepEqual(parse('9898n'), ast(0, 'data', BigInt(9898)));
+  t.deepEqual(parse('98_9_8n'), ast(0, 'data', BigInt(9898)));
   t.deepEqual(parse(`{}`), ast(0, 'record', []));
   t.deepEqual(parse(`[]`), ast(0, 'array', []));
   t.deepEqual(