ProseMirror Notes Editor

This skill documents how the notes editor works, common pitfalls, and how to debug issues.

Key Files

Critical Concepts

1. Atom Nodes

The wiki_link node is defined as atom: true:

const wikiLinkNodeSpec: NodeSpec = {
    group: "inline",
    inline: true,
    atom: true,  // <-- This is critical!
    attrs: { href: { default: "" }, title: { default: "" } },
    // ...
};

What atom: true means:

• The node is treated as a single indivisible unit
• Cursor cannot be placed inside it
• textBetween() represents it based on the leafText parameter, NOT its content

2. The textBetween Trap

node.textBetween(from, to, blockSeparator?, leafText?) extracts text, but:

• Text nodes: Returns their text content
• Atom nodes: Returns the leafText parameter value (default: empty string)

THE BUG THAT BREAKS EVERYTHING:

// BAD - wiki_link becomes "\n", breaking regex matching
const text = node.textBetween(0, node.content.size, undefined, "\n");

// GOOD - wiki_link becomes "", regex works correctly
const text = node.textBetween(0, node.content.size, undefined, "");

If you use "\n" as leafText, a todo like:

- [ ] text [[link]] more

Becomes:

"- [ ] text \n more"

And TODO_REGEX = /^(\s)- \[([ xX])\] ?(.)$/ fails because:

• (.*) stops at the newline
• $ doesn't match (there's still \n more remaining)

3. Preserving Inline Nodes During Edits

When modifying a line that contains inline nodes (wiki_link, marks, etc.):

BAD - Destroys inline nodes:

// This replaces entire line with plain text
transaction.replaceWith(
    range.lineStart,
    range.lineEnd,
    state.schema.text(newText)  // <-- Creates plain text, destroys wiki_links!
);

GOOD - Preserves inline nodes:

// Only replace the specific character that needs to change
// For toggling checkbox: only replace the " " or "x" character
const checkboxPos = range.lineStart + indent.length + 3;  // Position of checkbox char
transaction.replaceWith(
    checkboxPos,
    checkboxPos + 1,
    state.schema.text(newChecked)  // Just " " or "x"
);

4. How Todo Decorations Work

The todo system uses ProseMirror decorations to:

1. Hide the raw - [ ] markdown
2. Show a checkbox widget in its place
3. Apply styling classes to the paragraph

function buildTodoDecorations(doc: PMNode): DecorationSet {
    doc.descendants((node, pos) => {
        // Get text content (atom nodes become empty string)
        const text = node.textBetween(0, node.content.size, undefined, "");

        // Match todo pattern
        const match = text.match(TODO_REGEX);
        if (match) {
            // 1. Node decoration for styling
            decorations.push(Decoration.node(pos, pos + node.nodeSize, {
                class: "todo-paragraph"
            }));

            // 2. Inline decoration to hide "- [ ] "
            decorations.push(Decoration.inline(markerStart, markerEnd, {
                class: "todo-marker-hidden"
            }));

            // 3. Widget decoration for checkbox
            decorations.push(Decoration.widget(markerStart,
                () => createCheckboxWidget(isChecked)
            ));
        }
    });
}

Debugging Checklist

When todos/wikilinks aren't working:

1. Check textBetween calls - Are they using problematic leafText values?
2. Check document structure - Use console.log(JSON.stringify(node.toJSON(), null, 2))
3. Check if decorations apply - Inspect element to see if todo-paragraph class is present
4. Check serialization - Does saving and reloading preserve content?

Common Patterns

Getting Text for Regex Matching

// Always use empty string for leafText when matching patterns
// This applies to BOTH node.textBetween() and state.doc.textBetween()
const text = node.textBetween(0, node.content.size, undefined, "");
const lineText = state.doc.textBetween(start, end, undefined, "");

ALL functions that use textBetween for regex matching must include leafText: "":

• toggleTodoWithinRange
• handleTodoBackspace
• handleTodoEnter
• handleTodoClick
• handleTodoIndent
• handleTodoOutdent
• buildTodoDecorations

Safe Todo Toggle

// For existing todos, only replace the checkbox character
if (isTodoLine) {
    const checkboxPos = lineStart + indent.length + 3;
    tr.replaceWith(checkboxPos, checkboxPos + 1, schema.text(newState));
}

Inserting Inline Nodes

// When inserting wiki_link via autocomplete
const wikiLinkNode = schema.nodes.wiki_link.create({
    href: noteName,
    title: displayTitle
});
tr.replaceWith(from, to, [wikiLinkNode, schema.text(" ")]);

The Todo Regex Patterns

// Standalone paragraph todo: "- [ ] text" or "- [x] text"
const TODO_REGEX = /^(\s*)- \[([ xX])\] ?(.*)$/;

// List item todo (inside list_item): "[ ] text" or "[x] text"
const LIST_TODO_REGEX = /^\[([ xX])\] ?(.*)$/;

// Trigger pattern for creating new todo
const TRIGGER_REGEX = /^(\s*)(-\s*)?\[\]$/;

// Empty todo detection
const EMPTY_TODO_REGEX = /^(\s*)- \[([ xX])\]\s*$/;

CRITICAL: Handle BOTH Todo Formats

There are TWO todo formats that must be handled in every keyboard handler:

Every handler must check BOTH patterns:

• handleTodoBackspace - must handle both formats
• handleTodoEnter - must handle both formats
• toggleTodoWithinRange - must handle both formats
• handleTodoClick - checks both with text.match(TODOREGEX) \|\| text.match(LISTTODO_REGEX)

Keyboard Handler Behaviors

Enter Key (handleTodoEnter)

When pressing Enter on a todo line:

1. Empty todo → Remove the marker, leave empty line
2. Todo with content → Create new empty todo below

// Always create a NEW empty todo (don't try to split content)
// This avoids position mapping issues with inline nodes
const newTodoContent = `${indent}- [ ] `;

Backspace Key (handleTodoBackspace)

When pressing Backspace:

1. Cursor at content start → Remove the todo marker
2. Empty todo, cursor anywhere after marker → Remove the marker

// Check if todo is empty/whitespace-only
const isEmptyTodo = !contentText.trim();

// Handle backspace if:
// 1. Cursor is at the very start of content, OR
// 2. Todo is empty and cursor is at or after content start
const atContentStart = cursorOffsetInLine === contentStartOffset;
const inEmptyTodo = isEmptyTodo && cursorOffsetInLine >= contentStartOffset;

Marker length calculations:

• Standalone todo - [ ] : marker is 6 chars (with trailing space) or 5 chars (without)
• List item todo [ ] : marker is 4 chars (with trailing space) or 3 chars (without)

Position Calculations

Document Positions vs Text Positions

• Document positions: Used by ProseMirror for cursor, selections, ranges
• Text positions: Character indices in strings from textBetween()

For plain text, these are equivalent. But with atom nodes (wiki_link):

• Atom node takes 1 document position
• Atom node takes 0 text characters (with leafText: "")

This can cause mismatches when:

// Document position-based
const cursorOffsetInLine = selection.from - paragraphRange.lineStart;

// Text position-based
const contentStartOffset = indent.length + markerLength;

Solution: For complex operations, work with document positions directly or avoid slicing text based on cursor position.

Testing Changes

After modifying todo/wikilink code:

1. Basic todo: Create - [ ] test, verify checkbox renders
2. With wikilink: Add [[link]] via autocomplete, verify checkbox still works
3. Toggle: Click checkbox, verify wikilink preserved
4. Enter on todo: Press Enter, verify new checkbox created (not bullet)
5. Enter on empty todo: Press Enter, verify marker removed
6. Backspace on empty todo: Press Backspace, verify marker removed
7. Indented todos: Test all above with indented todos (2+ spaces)
8. List item todos: Test with [ ] text format inside lists
9. Save/reload: Verify content persists correctly