mermaid-js/mermaid · error · Error

" " has invalid value: . Negative values are not allowed in…

Error message

"${label}" has invalid value: ${value}. Negative values are not allowed in pie charts. All slice values must be >= 0.

What it means

Thrown by addSection in the pie db when a slice's value is less than zero. Pie chart slices represent non-negative quantities (counts, percentages); a negative slice has no meaningful geometry and is rejected before insertion into the sections map. The check fires on any negative numeric value regardless of label.

Solutions

Replace the negative value with a non-negative number (>= 0).
If negatives are semantically meaningful (e.g. net change), choose a different chart type — pie cannot represent them.
Sanitize imported data by clamping negatives to 0 or filtering them out before rendering.
Validate the value in your data layer before passing it to mermaid.

Example fix

// before
pie title Sales
  "Returns" : -12
  "New" : 50

// after
pie title Sales
  "Returns" : 12
  "New" : 50

Defensive patterns

Strategy: validation

Validate before calling

function sanitizePieValue(label: string, value: number): number {
  if (value < 0) {
    throw new Error(`Slice '${label}' has negative value ${value}; pie values must be >= 0`);
  }
  return value;
}

Type guard

function isNonNegative(value: number): boolean {
  return Number.isFinite(value) && value >= 0;
}

Try / catch

try {
  await mermaid.render('g', diagramText);
} catch (e) {
  if (e instanceof Error && /Negative values are not allowed in pie charts/.test(e.message)) {
    showUserError('Pie chart slices cannot have negative values. Use a non-negative number or a different chart type.');
  } else throw e;
}

Prevention

Validate data values are >= 0 before building the pie diagram text.
Filter or clamp negatives in data pipelines that feed mermaid.
Choose a bar chart if negatives are semantically required.

When it happens

Trigger: Writing a pie diagram line with a negative number, e.g. 'pie title ... "Label" : -5'; feeding computed values where a subtraction underflows; CSV/data import that includes negatives.

Common situations: Data pipeline emitting negative deltas; author misunderstanding that pie values must be non-negative; typos entering a minus sign before a value.

Related errors

AI-assisted analysis of mermaid-js/mermaid@d93e9c88c0 (2026-08-12). Data as JSON: /api/errors/9a07128e84f96fcc. Report an issue: GitHub.

Appendix: source

Thrown at packages/mermaid/src/diagrams/pie/pieDb.ts:38

  showData: false,
  config: DEFAULT_PIE_CONFIG,
} as const;

let sections: Sections = DEFAULT_PIE_DB.sections;
let showData: boolean = DEFAULT_PIE_DB.showData;
const config: Required<PieDiagramConfig> = structuredClone(DEFAULT_PIE_CONFIG);

const getConfig = (): Required<PieDiagramConfig> => structuredClone(config);

const clear = (): void => {
  sections = new Map();
  showData = DEFAULT_PIE_DB.showData;
  commonClear();
};

const addSection = ({ label, value }: D3Section): void => {
  if (value < 0) {
    throw new Error(
      `"${label}" has invalid value: ${value}. Negative values are not allowed in pie charts. All slice values must be >= 0.`
    );
  }
  if (!sections.has(label)) {
    sections.set(label, value);
    log.debug(`added new section: ${label}, with value: ${value}`);
  }
};

const getSections = (): Sections => sections;

const setShowData = (toggle: boolean): void => {
  showData = toggle;
};

const getShowData = (): boolean => showData;

export const db: PieDB = {

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