expose getOpt error handling to frontend

TODO

@@ -1,9 +1,6 @@
 - path to event listener:
 
   - card fields (vars maybe not needed yet?)
-    - get field command
-      - current card in state
-      - command
     - set field command
       - formatter helper for debug page
         - unit test

src/3x5.ts

@@ -1,8 +1,8 @@
-import { Card, CardVm, GetField } from './lib/card';
-import { ALL as HTML } from './lib/html';
-import { parse } from './parser';
-import { runNoctl, Vm } from './vm';
-import { AsHtml, AsText, TextPiece } from './words';
+import { Card, CardVm, GetField } from "./lib/card";
+import { ALL as HTML } from "./lib/html";
+import { parse } from "./parser";
+import { runNoctl, Vm } from "./vm";
+import { AsHtml, AsText, TextPiece } from "./words";
 
 /**
  * Updates a card's fields
@@ -65,7 +65,7 @@ title "Hello, World!"
 const codeInput = document.createElement("textarea");
 Object.assign(codeInput.style, TEXTAREA_STYLE, { height: "20em" });
 codeInput.value = String.raw`
-h1 "Hello, World!"
+h1 [get title]
 para [2 + 2]
 block {
     This is a paragraph of text, with one [b bold] word. Yes, this means there has to be some magic in text processing... <b>this</b> won't work.

src/lib/card.ts

@@ -1,6 +1,6 @@
-import { Vm } from '../vm';
-import { TextPiece } from '../words';
-import { getOpt } from './options';
+import { Vm } from "../vm";
+import { TextPiece } from "../words";
+import { getOpt } from "./options";
 
 /**
  * Basic unit of information, also an "actor" in the programming system
@@ -19,7 +19,6 @@ export type CardVm = Vm<{
 }>;
 
 export function GetField(vm: CardVm, argv: TextPiece[]): TextPiece {
-  const [{ error = false }, fieldName] = getOpt(argv, { min: 1, max: 1 });
-  // TODO: handle error
-  return { text: vm.card.fields[fieldName] ?? "" };
+  const [{ error }, fieldName] = getOpt(argv, { $min: 1, $max: 1 });
+  return { text: vm.card.fields[fieldName] ?? error ?? "" };
 }