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table-column-count

Disallow data rows in a GitHub Flavored Markdown table from having more cells than the header row.

Background

In GitHub Flavored Markdown tables, rows should maintain a consistent number of cells. While variations are sometimes tolerated, data rows having more cells than the header can lead to lost data or rendering issues. This rule prevents data rows from exceeding the header's column count.

Rule Details

Important

This rule relies on the table AST node, typically available when using a GFM-compatible parser (e.g., language: "markdown/gfm").

This rule is triggered if a data row in a GFM table contains more cells than the header row. It does not flag rows with fewer cells than the header.

Examples of incorrect code for this rule:

<!-- eslint markdown/table-column-count: "error" -->

| Head1 | Head2 |
| ----- | ----- |
| R1C1  | R1C2  | R2C3  | <!-- This data row has 3 cells, header has 2 -->

| A |
| - |
| 1 | 2 | <!-- This data row has 2 cells, header has 1 -->

Examples of correct code for this rule:

<!-- eslint markdown/table-column-count: "error" -->

<!-- Standard correct table -->
| Header | Header |
| ------ | ------ |
| Cell   | Cell   |
| Cell   | Cell   |

<!-- Data row with fewer cells than header (VALID for this rule) -->
<!-- Rows with fewer cells are valid because they render correctly and no data is lost -->
| Header | Header | Header |
| ------ | ------ | ------ |
| Cell   | Cell   |        |

<!-- Table with some empty cells (VALID for this rule) -->
<!-- Missing cells are treated as empty and don't cause rendering issues -->
| Col A | Col B | Col C |
| ----- | ----- | ----- |
| 1     |       | 3     |
| 4     | 5     |

<!-- Single column table -->
| Single Header |
| ------------- |
| Single Cell   |

Options

The following options are available on this rule:

  • checkMissingCells: boolean - When set to true, the rule will also flag rows that have fewer cells than the header row. (default: false)

Examples of incorrect code when configured as "table-column-count": ["error", { checkMissingCells: true }]:

<!-- eslint markdown/table-column-count: ["error", { checkMissingCells: true }] -->

<!-- Data row with fewer cells than header -->
| Col A | Col B | Col C |
| ----- | ----- | ----- |
| 1     |       | 3     |
| 4     | 5     |

When Not To Use It

If you intentionally create Markdown tables where data rows are expected to contain more cells than the header, and you have a specific (perhaps non-standard) processing or rendering pipeline that handles this scenario correctly, you might choose to disable this rule. However, adhering to this rule is recommended for typical GFM rendering and data consistency.

Prior Art