From 319861792365fa3db92824079d0810b27d47f01b Mon Sep 17 00:00:00 2001
From: dstoc <539597+dstoc@users.noreply.github.com>
Date: Sat, 16 Nov 2024 17:14:15 +1100
Subject: [PATCH] fix: Cursor movement in/out of transclusions

* If the transcluded content was not at the end of its document then
errors in findFinalEditable prevented some movements.
* Transclusions did not handle -0 focus offset (start of last line).
---
 src/copy-paste-util.ts          |  3 +--
 src/markdown/transclusion.ts    |  7 +++---
 src/markdown/view-model-util.ts | 12 ++++++++---
 tests/edit_test.ts              | 38 +++++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/src/copy-paste-util.ts b/src/copy-paste-util.ts
index 2dc63c4e..bad4f91f 100644
--- a/src/copy-paste-util.ts
+++ b/src/copy-paste-util.ts
@@ -14,7 +14,6 @@ import {
   cloneNode,
   compareDocumentOrder,
   dfs,
-  findFinalEditable,
   performLogicalInsertion,
   removeDescendantNodes,
 } from './markdown/view-model-util.js';
@@ -30,7 +29,7 @@ export function insertMarkdown(markdown: string, node: ViewModelNode) {
   const newInlineNodes = newNodes
     .flatMap((node) => [...dfs(node, node)])
     .filter(isInlineViewModelNode);
-  const newFocus = findFinalEditable(newNodes[0]);
+  const newFocus = newInlineNodes.at(-1);
   performLogicalInsertion(node, newNodes);
   return {newFocus, newInlineNodes};
 }
diff --git a/src/markdown/transclusion.ts b/src/markdown/transclusion.ts
index c1ddb384..c0c6f014 100644
--- a/src/markdown/transclusion.ts
+++ b/src/markdown/transclusion.ts
@@ -85,10 +85,11 @@ export class MarkdownTransclusion extends LitElement implements SigpropHost {
     if (!this.hostContext) return;
     if (!this.root) return;
     if (this.hostContext.focusNode !== this.node) return;
+    const offset = this.hostContext.focusOffset ?? -1;
     const node =
-      (this.hostContext.focusOffset ?? -1) >= 0
-        ? findNextEditable(this.root, this.root, true)
-        : findFinalEditable(this.root, true);
+      offset < 0 || Object.is(offset, -0)
+        ? findFinalEditable(this.root, this.root, true)
+        : findNextEditable(this.root, this.root, true);
     this.markdownRenderer.hostContext.focusNode = node ?? undefined;
     this.markdownRenderer.hostContext.focusOffset =
       this.hostContext.focusOffset;
diff --git a/src/markdown/view-model-util.ts b/src/markdown/view-model-util.ts
index 17cc6008..c14956f0 100644
--- a/src/markdown/view-model-util.ts
+++ b/src/markdown/view-model-util.ts
@@ -18,7 +18,9 @@ import {
   isInlineViewModelNode,
   type InlineViewModelNode,
   type MaybeViewModelNode,
-  type ViewModelNode, viewModel} from './view-model-node.js';
+  type ViewModelNode,
+  viewModel,
+} from './view-model-node.js';
 import {MarkdownNode} from './node.js';
 
 export function swapNodes(node1: ViewModelNode, node2: ViewModelNode) {
@@ -160,11 +162,12 @@ export function findNextEditable(
 // TODO: why doesn't this return Editable?
 export function findFinalEditable(
   node: ViewModelNode,
+  root: ViewModelNode,
   include = false,
 ): InlineViewModelNode | null {
   let result: InlineViewModelNode | null = null;
   if (include && isInlineViewModelNode(node)) result = node;
-  for (const next of dfs(node)) {
+  for (const next of dfs(node, root)) {
     if (isInlineViewModelNode(next)) result = next;
   }
   return result;
@@ -175,7 +178,10 @@ export function findNextDfs<T extends ViewModelNode>(
   root: ViewModelNode,
   predicate: (node: ViewModelNode) => node is T,
 ) {
-  for (const next of dfs(node, root[viewModel].parent)) {
+  for (const next of dfs(
+    node,
+    root[viewModel].nextSibling ?? root[viewModel].parent,
+  )) {
     if (next !== node && predicate(next)) return next;
   }
   return null;
diff --git a/tests/edit_test.ts b/tests/edit_test.ts
index e9ab006f..0d7c3bf1 100644
--- a/tests/edit_test.ts
+++ b/tests/edit_test.ts
@@ -90,6 +90,44 @@ test.describe('editing', () => {
 
       `);
     });
+    test('follow caret movements in and out', async ({page}) => {
+      await page.keyboard.type('before');
+      await page.keyboard.press('Enter');
+      await page.keyboard.type('after');
+      await page.keyboard.press('Home');
+      await page.keyboard.press('ArrowUp');
+      await importFile('transclusion.md', '# transclusion\naaa');
+      await state.main.runCommand('insert transclusion', 'transclusion');
+      await state.main.host
+        .locator('md-transclusion')
+        .waitFor({state: 'visible'});
+      await page.keyboard.press('ArrowDown');
+      await page.keyboard.press('ArrowDown');
+      await page.keyboard.type('1');
+      await page.keyboard.press('ArrowDown');
+      await page.keyboard.type('2');
+      await page.keyboard.press('ArrowUp');
+      await page.keyboard.type('3');
+      await page.keyboard.press('ArrowUp');
+      await page.keyboard.press('ArrowUp');
+      await page.keyboard.type('4');
+      expect(await exportMarkdown('test')).toMatchPretty(`
+        # test
+        bef4ore
+
+        \`\`\`tc
+        transclusion
+        \`\`\`
+
+        a2fter
+
+      `);
+      expect(await exportMarkdown('transclusion')).toMatchPretty(`
+        # transclusion
+        1a3aa
+
+      `);
+    });
     test('can be inserted and deleted', async ({page}) => {
       await page.keyboard.type('test');
       await importFile('transclusion.md', '# transclusion\n');