Config reference

The wit.sources.json schema, the formats a source can return, the built-in env source, and the --allow-exec rules. Source: packages/cli/src/data-sources.ts, packages/runtime/src/data-loader.ts.

wit.sources.json

source

{
  "sources": {
    "sales": {
      "run": ["python3", "scripts/sales.py", "{{region}}"],
      "format": "csv",
      "timeoutMs": 30000
    }
  }
}

result

{ "sources": { "sales": { "run": ["python3", "scripts/sales.py", "{{region}}"], "format": "csv", "timeoutMs": 30000 } } }

Fields
Field	Required	Meaning	Default
sources	yes	object of aliases	—
ALIAS.run	yes	non-empty argv array; the first element is the program	—
ALIAS.format	no	one of the seven formats below	json
ALIAS.timeoutMs	no	kill the program after this many ms	30000

Pass it with --sources wit.sources.json to wit build or wit check.
run is resolved relative to the sources file, and the program runs in that file's directory.
{{name}} in a run token becomes that @load parameter's value; a missing one becomes empty.
Output is capped at 16 MB. A non-zero exit, a timeout or a parse failure is E_LOAD_FAILED at the @load.
Config errors: expected a top-level "sources" object, source "run" must be a non-empty argv array. JSON only.

Formats

What stdout becomes
Format	Value
json	parsed JSON; empty output is null
csv	a collection of records keyed by the first row
tsv	the same with tabs
lines	a collection of the non-empty lines
text	the output as one string
svg	the output as one string
html	the output as one string

CSV and TSV follow RFC 4180: a quoted field may hold the separator, a doubled quote is a quote, and a quoted field may span lines. Loaded strings are text — never read as Wit markup.

Using a source

@load(as: rows, region: North) sales load@

@table(rows: @rows)

load parameters
Form	Effect
body text	the alias to load
from: ALIAS	the alias when there is no body
as: NAME	name the resulting data definition; default is the alias
any other KEY: VALUE	passed to the program

@load(from: sales, as: rows, region: North) needs no close. A @load works at the top level, in a node body and in referenced files; it must stand on its own lines, not inside a sentence. Several files may load the same alias — that is one definition, not a duplicate. No alias at all is E_LOAD_FAILED (@load needs an alias).

The env source

Built in; needs no config and no --allow-exec. It returns the process environment merged with the --env dotenv file, as a record.

@load env load@

Built by @env.USER.

The dotenv reader takes KEY=value lines, treats # lines as comments, strips surrounding quotes and skips blank or key-less lines.

Security

Rules
Rule	Behaviour
no --allow-exec	any source other than env fails: running programs is disabled; pass --allow-exec
unknown alias	no source configured for alias NAME
working directory	the sources file's directory
child environment	the process environment plus --env
parameters	substituted into run tokens and sent on stdin as JSON