mermaid-js/mermaid · error

No nodes available to create tree

Error message

No nodes available to create tree

What it means

Thrown by convertToDualTreeFormat when it cannot find a root node AND nodes.length === 0. In practice this is a defensive duplicate of the empty-nodes guard at line 28: executeTidyTreeLayout already rejects empty nodes before calling convertToDualTreeFormat, so reaching this throw requires calling convertToDualTreeFormat directly (it is a private, non-exported helper) with an empty array.

Source

Thrown at packages/mermaid-layout-tidy-tree/src/layout.ts:108

  const children = new Map<string, string[]>();
  const parents = new Map<string, string>();

  edges.forEach((edge) => {
    const parentId = edge.start;
    const childId = edge.end;

    if (parentId && childId) {
      if (!children.has(parentId)) {
        children.set(parentId, []);
      }
      children.get(parentId)!.push(childId);
      parents.set(childId, parentId);
    }
  });

  const rootNodeData = nodes.find((node) => !parents.has(node.id));
  if (!rootNodeData && nodes.length === 0) {
    throw new Error('No nodes available to create tree');
  }

  const actualRoot = rootNodeData ?? nodes[0];

  const rootNode: TidyTreeNode = {
    id: actualRoot.id,
    width: actualRoot.width ?? 100,
    height: actualRoot.height ?? 50,
    _originalNode: actualRoot,
  };

  const rootChildren = children.get(actualRoot.id) ?? [];
  const leftChildren: string[] = [];
  const rightChildren: string[] = [];

  rootChildren.forEach((childId, index) => {
    if (index % 2 === 0) {
      leftChildren.push(childId);

View on GitHub (pinned to d93e9c88c0)

Solutions

1. Do not call convertToDualTreeFormat directly; use executeTidyTreeLayout.
2. If testing the helper internally, supply at least one node.
3. Treat a real occurrence as a sign that the earlier guard in executeTidyTreeLayout was bypassed.

// Ensure convertToDualTreeFormat is never reached with empty nodes:
if (!data.nodes || data.nodes.length === 0) {
  throw new Error('Skipping layout: no nodes');
}
const result = await executeTidyTreeLayout(data);

function hasAtLeastOneNode(data: unknown): data is { nodes: { id: string }[] } {
  return Array.isArray((data as any).nodes) && (data as any).nodes.length > 0;
}

When it happens

Trigger: Only reachable if convertToDualTreeFormat is invoked with a zero-length nodes array outside the normal executeTidyTreeLayout entry path. Through the public API, error [0] fires first and this branch is never reached.

Common situations: Almost never seen by external callers; surfaces only during internal refactors or tests that call convertToDualTreeFormat directly with stubbed data.

Related errors

• No nodes found in layout data
• Nodes array is required in layout data
• Layout data is required
• Configuration is required in layout data
• Edges array is required in layout data

AI-assisted analysis of mermaid-js/mermaid@d93e9c88c0 (2026-08-12). Data as JSON: /api/errors/151fc6be7e7703d0. Report an issue: GitHub.