Method validateExpressionSizes

pkg/workflow/runtime_validation.go:64–105

validateExpressionSizes validates that no expression values in the generated YAML exceed GitHub Actions limits. GitHub Actions enforces a 21,000-character limit on YAML string values that contain template expressions (${{ }}). This check covers two cases: 1. Single-line values: each YAML line is c

(yamlContent string)

//     block contains at least one ${{ }} expression AND its total length exceeds 21,000
//     characters, GitHub Actions rejects the workflow with "Exceeded max expression length".
func (c *Compiler) validateExpressionSizes(yamlContent string) error {
	lines := strings.Split(yamlContent, "\n")
	runtimeValidationLog.Printf("Validating expression sizes: yaml_lines=%d, max_size=%d", len(lines), MaxExpressionSize)
	maxSize := MaxExpressionSize

	for lineNum, line := range lines {
		// Check the line length (actual content that will be in the YAML)
		if len(line) > maxSize {
			// Extract the key/value for better error message
			trimmed := strings.TrimSpace(line)
			key := ""
			if colonIdx := strings.Index(trimmed, ":"); colonIdx > 0 {
				key = strings.TrimSpace(trimmed[:colonIdx])
			}

			// Format sizes for display
			actualSize := console.FormatFileSize(int64(len(line)))
			maxSizeFormatted := console.FormatFileSize(int64(maxSize))

			var errorMsg string
			if key != "" {
				errorMsg = fmt.Sprintf("expression value for %q (%s) exceeds maximum allowed size (%s) at line %d. GitHub Actions has a 21KB limit for expression values including environment variables. Consider chunking the content or using artifacts instead.",
					key, actualSize, maxSizeFormatted, lineNum+1)
			} else {
				errorMsg = fmt.Sprintf("line %d (%s) exceeds maximum allowed expression size (%s). GitHub Actions has a 21KB limit for expression values.",
					lineNum+1, actualSize, maxSizeFormatted)
			}

			return errors.New(errorMsg)
		}
	}

	// Check multi-line YAML block scalars that contain template expressions.
	// A run: | or any other block-scalar value is a single string from GitHub Actions'
	// perspective; if it contains ${{ }} AND is longer than 21,000 characters the
	// runner rejects it with "Exceeded max expression length".
	if err := validateBlockScalarExpressionSizes(lines, maxSize); err != nil {
		return err
	}

	return nil
}

// validateBlockScalarExpressionSizes scans the YAML lines for multi-line block scalars
// (literal | or folded >) and returns an error when any such block both contains a