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⚙️ Mold Defaults

A mold script can embed default CLI options via # fimod: comment directives. This makes scripts self-describing — callers don't need to remember which format or options a script expects.

Where to put directives

Directives must appear at the very top of the file, before any code.

# fimod: input-format=csv, output-format=json
# fimod: csv-delimiter=;
def transform(data, args, env, headers):
    return [{"name": row["name"], "age": int(row["age"])} for row in data]

Running this with just fimod s -i data.csv -m script.py automatically uses ; as the delimiter.

📋 Supported directives

Directive Type Description
input-format=<fmt> value Input format (json, ndjson, yaml, toml, csv, txt, lines)
output-format=<fmt> value Output format
csv-delimiter=<char> value CSV input delimiter character
csv-output-delimiter=<char> value CSV output delimiter character
csv-header=<cols> value Explicit column names (comma-separated)
csv-no-input-header flag Input has no header row
csv-no-output-header flag Don't write header in output
raw-mode=<mode> value Raw output mode: no-quote (strings without JSON quotes) or binary (raw bytes)
description=<text> value One-line description shown by fimod mold list

📏 Priority and parsing rules

CLI always wins

Explicit CLI arguments always override mold defaults.

  • Directives are read from the top of the file — scanning stops at the first non-comment, non-blank line
  • Multiple key-value pairs can appear on the same # fimod: line, comma-separated
  • Unknown keys are silently ignored
  • Directives in -e inline expressions are never parsed

💡 Complete example

# fimod: input-format=csv
# fimod: output-format=json
# fimod: csv-delimiter=;
# fimod: csv-no-input-header
# fimod: output-format=json-compact
def transform(data, args, env, headers):
    # data = [{"col0": ..., "col1": ...}, ...]
    return [{"name": row["col0"], "value": int(row["col1"])} for row in data]

# ✅ Use defaults
fimod s -i data.csv -m script.py

# 🔀 Override output format at call time
fimod s -i data.csv -m script.py --output-format yaml