From e970ef762cf371d8b9faefd38b26bc337dd2135e Mon Sep 17 00:00:00 2001
From: Robert Balicki <robert.balicki@gmail.com>
Date: Wed, 1 Jan 2025 15:41:19 +0900
Subject: [PATCH] fix a few TS errors in compileTag

---
 libs/isograph-babel-plugin/compileTag.js | 26 +++++++++++++++---------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/libs/isograph-babel-plugin/compileTag.js b/libs/isograph-babel-plugin/compileTag.js
index 17d5ddb64..4f56f1c6a 100644
--- a/libs/isograph-babel-plugin/compileTag.js
+++ b/libs/isograph-babel-plugin/compileTag.js
@@ -17,11 +17,15 @@ function compileTag(t, path, config) {
       // This throws if the tag is invalid
       compileImportStatement(t, path, type, field, 'entrypoint', config);
     } else if (keyword === 'field') {
-      if (
-        t.isCallExpression(path.parentPath.node) &&
-        path.parentPath.node.arguments.length === 1
-      ) {
-        path.parentPath.replaceWith(path.parentPath.node.arguments[0]);
+      if (t.isCallExpression(path.parentPath.node)) {
+        const firstArg = path.parentPath.node.arguments[0];
+        if (path.parentPath.node.arguments.length === 1 && firstArg != null) {
+          path.parentPath.replaceWith(firstArg);
+        } else {
+          throw new Error(
+            'Invalid iso tag usage. The iso function should be passed at most one argument.',
+          );
+        }
       } else {
         path.replaceWith(
           t.arrowFunctionExpression([t.identifier('x')], t.identifier('x')),
@@ -45,26 +49,28 @@ const typeAndFieldRegex = new RegExp(
  * @param {babel.NodePath<babel.types.CallExpression>} path
  *  */
 function getTypeAndField(path) {
-  if (path.node.arguments.length !== 1) {
+  const firstArg = path.node.arguments[0];
+  if (path.node.arguments.length !== 1 || firstArg == null) {
     throw new Error(
       `BabelPluginIsograph: Iso invocation require one parameter, found ${path.node.arguments.length}`,
     );
   }
 
-  if (path.node.arguments[0].type !== 'TemplateLiteral') {
+  if (firstArg.type !== 'TemplateLiteral') {
     throw new Error(
       'BabelPluginIsograph: Only template literals are allowed in iso fragments.',
     );
   }
 
-  const quasis = path.node.arguments[0].quasis;
-  if (quasis.length !== 1) {
+  const quasis = firstArg.quasis;
+  const firstQuasi = quasis[0];
+  if (quasis.length !== 1 || firstQuasi == null) {
     throw new Error(
       'BabelPluginIsograph: Substitutions are not allowed in iso fragments.',
     );
   }
 
-  const content = quasis[0].value.raw;
+  const content = firstQuasi.value.raw;
   const typeAndField = typeAndFieldRegex.exec(content);
 
   const keyword = typeAndField?.[1];