GitHub Actions "Matrix vector 'x' does not contain any values"

By Daniel Zoghalchali·Latchkey

A matrix dimension expanded to no values - it is null, an empty list, or a fromJSON of an empty/blank string - so the matrix has nothing to iterate and the job cannot be generated.

What this error means

The workflow fails with "Matrix vector 'node' does not contain any values", naming a dimension whose list is empty. Common with dynamic matrices built from a previous job output.

Error: Matrix vector 'node' does not contain any values

Common causes

Static dimension is empty or null

A matrix key mapped to [], null, or left blank has no values to expand, which is rejected.

Dynamic matrix produced an empty array

When the matrix comes from fromJSON(needs.x.outputs.list), an upstream job that emitted "[]" or an empty string yields a vector with no values.

How to fix it

Ensure each dimension has values

Give static dimensions a non-empty list, and guard dynamic matrices against an empty array.

strategy:
  matrix:
    node: [18, 20, 22]   # non-empty list

Handle empty dynamic matrices

1. Have the producing job always emit a valid non-empty JSON array, or skip the matrix job when empty.
2. Add an if: on the matrix job that checks the upstream output is not "[]".
3. Echo the JSON in the producer to confirm it is a non-empty array before fromJSON.

How to prevent it

• Keep every static matrix dimension a non-empty list.
• Guard dynamic matrices so an empty result skips rather than fails.
• Validate producer output is valid non-empty JSON before fromJSON.

Frequently asked questions

Related guides

References

• GitHub Actions documentation
• Workflow syntax for GitHub Actions