Prevent empty index access ([])

Author: g. nicholas d'andrea

Diff for: packages/parse-mapping-lookup/src/grammar.ts

@@ -41,8 +41,8 @@ export const definitions: Definitions<Forms> = {
 
   value: ({ construct }) =>
     noCharOf("]").pipe(
-      many(),
-      map(characters => construct({ contents: characters.join("") }))
+      then(noCharOf("]").pipe(many())),
+      map(([first, rest]) => construct({ contents: [first, ...rest].join("") }))
     ),
 
   indexAccess: ({ construct, tie }) =>

Diff for: packages/parse-mapping-lookup/src/parser.spec.ts

@@ -86,6 +86,12 @@ const testCases = [
       position: 2
     }
   },
+  {
+    expression: `m[1].s[]`,
+    trace: {
+      position: 7
+    }
+  },
   {
     expression: `m[hex"deadbeef"]`,
     value: expression({