Improve error UX

Fix syntax error highlight
Add GitHub link

Author: mbolis

index.html

@@ -58,6 +58,13 @@
       </div>
       <pre id=out></pre>
     </div>
+    <div id=useful_links>
+      <a target=_blank rel=noreferrer href=https://github.com/mbolis/line.script title="Find me on GitHub">
+        <svg viewBox="0 0 438.549 438.549">
+          <path fill="currentColor" d="M409.132 114.573c-19.608-33.596-46.205-60.194-79.798-79.8-33.598-19.607-70.277-29.408-110.063-29.408-39.781 0-76.472 9.804-110.063 29.408-33.596 19.605-60.192 46.204-79.8 79.8C9.803 148.168 0 184.854 0 224.63c0 47.78 13.94 90.745 41.827 128.906 27.884 38.164 63.906 64.572 108.063 79.227 5.14.954 8.945.283 11.419-1.996 2.475-2.282 3.711-5.14 3.711-8.562 0-.571-.049-5.708-.144-15.417a2549.81 2549.81 0 01-.144-25.406l-6.567 1.136c-4.187.767-9.469 1.092-15.846 1-6.374-.089-12.991-.757-19.842-1.999-6.854-1.231-13.229-4.086-19.13-8.559-5.898-4.473-10.085-10.328-12.56-17.556l-2.855-6.57c-1.903-4.374-4.899-9.233-8.992-14.559-4.093-5.331-8.232-8.945-12.419-10.848l-1.999-1.431c-1.332-.951-2.568-2.098-3.711-3.429-1.142-1.331-1.997-2.663-2.568-3.997-.572-1.335-.098-2.43 1.427-3.289 1.525-.859 4.281-1.276 8.28-1.276l5.708.853c3.807.763 8.516 3.042 14.133 6.851 5.614 3.806 10.229 8.754 13.846 14.842 4.38 7.806 9.657 13.754 15.846 17.847 6.184 4.093 12.419 6.136 18.699 6.136 6.28 0 11.704-.476 16.274-1.423 4.565-.952 8.848-2.383 12.847-4.285 1.713-12.758 6.377-22.559 13.988-29.41-10.848-1.14-20.601-2.857-29.264-5.14-8.658-2.286-17.605-5.996-26.835-11.14-9.235-5.137-16.896-11.516-22.985-19.126-6.09-7.614-11.088-17.61-14.987-29.979-3.901-12.374-5.852-26.648-5.852-42.826 0-23.035 7.52-42.637 22.557-58.817-7.044-17.318-6.379-36.732 1.997-58.24 5.52-1.715 13.706-.428 24.554 3.853 10.85 4.283 18.794 7.952 23.84 10.994 5.046 3.041 9.089 5.618 12.135 7.708 17.705-4.947 35.976-7.421 54.818-7.421s37.117 2.474 54.823 7.421l10.849-6.849c7.419-4.57 16.18-8.758 26.262-12.565 10.088-3.805 17.802-4.853 23.134-3.138 8.562 21.509 9.325 40.922 2.279 58.24 15.036 16.18 22.559 35.787 22.559 58.817 0 16.178-1.958 30.497-5.853 42.966-3.9 12.471-8.941 22.457-15.125 29.979-6.191 7.521-13.901 13.85-23.131 18.986-9.232 5.14-18.182 8.85-26.84 11.136-8.662 2.286-18.415 4.004-29.263 5.146 9.894 8.562 14.842 22.077 14.842 40.539v60.237c0 3.422 1.19 6.279 3.572 8.562 2.379 2.279 6.136 2.95 11.276 1.995 44.163-14.653 80.185-41.062 108.068-79.226 27.88-38.161 41.825-81.126 41.825-128.906-.01-39.771-9.818-76.454-29.414-110.049z"></path>
+        </svg>
+      </a>
+    </div>
   </div>
 
   <script type=module src=src/index.ts></script>

package-lock.json

@@ -318,13 +318,17 @@ function clearEditorMarks() {
 function markError(start: number, end: number, message?: string) {
   const startPos = editor.findPosH(CodeMirror.Pos(0, 0), start, "char", true);
   const endPos = editor.findPosH(CodeMirror.Pos(0, 0), end, "char", true);
-  editor.getDoc().markText(startPos, endPos, { css: "background: rgba(255,128,128,0.4)" })
+  markErrorPos(startPos, endPos, message);
+}
+function markErrorPos(start: CodeMirror.Position, end: CodeMirror.Position, message?: string) {
+  editor.getDoc().markText(start, end, { css: "background: rgba(255,128,128,0.4)" })
 
   if (message) {
     output.error(message);
   }
 }
 
+
 setupMainLoop();
 
 function setState(nextState: TransportState) {
@@ -399,13 +403,15 @@ function ensureRunning() {
     try {
       interpreter = new Interpreter(txtCode.value);
     } catch (err) {
-      console.error(err)
+      //console.error(err)
       setState("done");
 
-      const message = /(.*)\((\d+):(\d+)\)\s*$/.exec(err.message);
-      const startPos = CodeMirror.Pos(+message[2], +message[3]);
-      const token = editor.getTokenAt(startPos);
-      markError(token.start, token.end, message[1] + `'${token.string}'`);
+      const [, message, line, ch] = /(.*) \((\d+):(\d+)\)\s*$/.exec(err.message);
+      const startPos = CodeMirror.Pos(+line, +ch);
+      const token = editor.getTokenAt(startPos, true);
+      startPos.line--;
+      const endPos = { ...startPos, ch: startPos.ch + token.string.length };
+      markErrorPos(startPos, endPos, `${message} '${token.string}' (${line}:${ch})`);
 
       throw err;
     }

src/index.ts

@@ -572,4 +572,23 @@ button.naked {
 #help_dialog dd {
     margin-left: 1.25em;
     margin-bottom: 0.5em;
+}
+
+#useful_links {
+    display: inline-block;
+    padding: 0.25em;
+    line-height: 1;
+    position: absolute;
+    bottom: 0;
+    right: 0;
+}
+#useful_links > a {
+    color: inherit;
+    display: inline-block;
+    height: 32px;
+    width: 32px;
+    opacity: 0.25;
+}
+#useful_links > a:hover {
+    opacity: 1;
 }