From 38fff6ba4c959ef2ebdb6aa7bbc44657687a19cb Mon Sep 17 00:00:00 2001
From: Mike Barkmin <mike@barkmin.eu>
Date: Wed, 28 Oct 2026 17:37:04 +0100
Subject: [PATCH] Keep the indented lines under a line the parser does not
 recognise

---
 .changeset/kind-lines-stay.md                 |  5 ++++
 packages/struktolab/package.json              |  1 +
 .../src/common/pseudocode-parser.js           | 24 +++++++++++++++++++
 .../src/common/pseudocode-parser.test.js      | 17 +++++++++++++
 4 files changed, 47 insertions(+)
 create mode 100644 .changeset/kind-lines-stay.md
 create mode 100644 packages/struktolab/src/common/pseudocode-parser.test.js

diff --git a/.changeset/kind-lines-stay.md b/.changeset/kind-lines-stay.md
new file mode 100644
index 0000000..4b6ff7b
--- /dev/null
+++ b/.changeset/kind-lines-stay.md
@@ -0,0 +1,5 @@
+---
+"struktolab": patch
+---
+
+Keep the indented lines under a line the pseudocode parser does not recognise (e.g. `while x:` instead of `repeat while x:`); they follow it instead of disappearing
diff --git a/packages/struktolab/package.json b/packages/struktolab/package.json
index a8c377b..69e0c0d 100644
--- a/packages/struktolab/package.json
+++ b/packages/struktolab/package.json
@@ -30,6 +30,7 @@
   ],
   "scripts": {
     "dev": "BUILD_TARGET=editor vite build --watch",
+    "test": "node --test 'src/**/*.test.js'",
     "build": "BUILD_TARGET=core vite build && BUILD_TARGET=renderer vite build && BUILD_TARGET=editor vite build",
     "build:core": "BUILD_TARGET=core vite build",
     "build:renderer": "BUILD_TARGET=renderer vite build",
diff --git a/packages/struktolab/src/common/pseudocode-parser.js b/packages/struktolab/src/common/pseudocode-parser.js
index 22d2274..f7e2366 100644
--- a/packages/struktolab/src/common/pseudocode-parser.js
+++ b/packages/struktolab/src/common/pseudocode-parser.js
@@ -619,6 +619,12 @@ function mergeBlocks(lines, baseIndent, keywords) {
     }
 
     // --- TaskNode (default) ---
+    // A line no construct claims may still have an indented body (a typo in
+    // a keyword, say). Its lines follow the task rather than vanish, so they
+    // stay visible and can be fixed.
+    if (block.children.length > 0) {
+      tail = appendChain(mergeBlocks(block.children, baseIndent + 4, keywords), tail);
+    }
     tail = makeInsert({
       id: uid(), type: "TaskNode", text: text,
       followElement: tail,
@@ -628,6 +634,24 @@ function mergeBlocks(lines, baseIndent, keywords) {
   return tail;
 }
 
+/**
+ * Puts `tail` after the last element of `chain` (both InsertNode-rooted
+ * sequences, as mergeBlocks builds them).
+ */
+function appendChain(chain, tail) {
+  let parent = null;
+  let node = chain;
+  // Walk InsertNode → element → InsertNode … to the closing InsertNode.
+  while (node.followElement) {
+    parent = node.followElement;
+    if (parent.type === "Placeholder") return tail;
+    node = parent.followElement;
+  }
+  if (!parent) return tail;
+  parent.followElement = tail;
+  return chain;
+}
+
 /**
  * Parse pseudocode string into a struktog tree.
  * @param {string} source - The pseudocode
diff --git a/packages/struktolab/src/common/pseudocode-parser.test.js b/packages/struktolab/src/common/pseudocode-parser.test.js
new file mode 100644
index 0000000..95fade8
--- /dev/null
+++ b/packages/struktolab/src/common/pseudocode-parser.test.js
@@ -0,0 +1,17 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { KEYWORDS_EN, parsePseudocode } from "./pseudocode-parser.js";
+import { treeToPseudocode } from "./tree-to-pseudocode.js";
+
+const roundTrip = (code) => treeToPseudocode(parsePseudocode(code, KEYWORDS_EN), KEYWORDS_EN);
+
+test("keeps loops and their bodies", () => {
+  const code = 'repeat while x > 0:\n    x = x - 1\noutput("x")';
+  assert.equal(roundTrip(code), code);
+});
+
+test("keeps the body of a line it does not understand", () => {
+  // "while" alone is not a loop ("repeat while" is); its body used to vanish.
+  const out = roundTrip('while x > 0:\n    x = x - 1\n    output("x")\ny = 1');
+  assert.equal(out, 'while x > 0:\nx = x - 1\noutput("x")\ny = 1');
+});