Description

When using the pie chart in Mermaid.js:

• A slice with a value of 0 is rendered with a 0% label that overlaps the edge of the chart.
• A slice with a negative value causes a MermaidParseError with an unclear error message.
• The documentation does not mention these limitations, which may confuse users generating values dynamically.

Steps to reproduce

1. Open the Mermaid Live Editor
2. Paste the following diagram:

pie
  title Zero and Negative Values
  "Valid Slice" : 30
  "Zero Slice" : 0
  "Negative Slice" : -10

Actual Behavior

• Mermaid fails to render the diagram.
• Console shows a vague parser error:
  MermaidParseError: Parsing failed: unexpected character: - at offset: 81
• The reason (negative value) is not explained.

If "Negative Slice" is removed:

pie
  title Zero and Negative Values
  "Valid Slice" : 30
  "Zero Slice" : 0

• Diagram renders.
• The "Zero Slice" appears in the legend and shows a 0% label at the top, overlapping the chart's border.
• This creates misleading visuals in a data visualization.

Screenshots

1. Chart with awkward 0% label placement

2. Console error for negative value

Code Sample

Setup

• Mermaid version: 11.6.0
• Browser: Chrome 124
• OS: Windows 11

Suggested Solutions

For Negative Values:

• Reject them at parse time with a clear error message, such as: "Negative values are not allowed in pie charts. All slice values must be ≥ 0."

For Zero Values:

• Option 1: Exclude them from the chart entirely.
• Option 2: Render them without label, or place label inside the pie in a non-overlapping position.
• Option 3: Add support for a hideZeroSlices: true flag in config.

Documentation:
Update Pie Chart Docs to explain behavior for 0 and negative values.

Additional Context

No response