JSON Output

JSON Output

← Config-Env-Vars · Compat-V15 · error-codes

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--json is one persistent flag on the root command. It has no shorthand. A command either honours it or refuses it; it never prints text and calls that JSON.

nself <command> --json          # JSON mode
nself <command> --json=false    # explicitly off, same as leaving it out

nself <command> --help lists --json under Global Flags.

What ships today

• Refusal. --json on a command that cannot produce JSON fails before the command does any work: exit status 1, nothing on stdout, and a text error on stderr (see E402 below).
• Commands with their own JSON (legacy, such as status and version) keep printing it, unchanged.
• stdout and stderr. The monorepo notice (Detected monorepo layout…) goes to stderr when --json is on, so it never mixes into stdout. Without --json it stays on stdout.
• Plugins. A plugin-proxied command receives --json unchanged (nself sentry status --json passes --json to the plugin) and owns its output. The CLI's other global flags (--no-monorepo, --no-deprecation-warnings) are still stripped.
• Secrets. Commands that print secret values, such as nself secrets decrypt-on-deploy, have no JSON support, so JSON mode never emits them.

Commands that cannot produce JSON: E402

Every command has a JSON support value in the command registry (internal/canon/canon.yaml): envelope (the v1 envelope), legacy (its own bare JSON) or none. --json on a none command, or together with a flag whose JSON override is none, is refused:

$ nself restart --json
Error: [E402] nself restart does not support --json

The refusal happens before the command's own start-up work, so nothing is restarted, fetched or cached. The bare nself --json is refused the same way.

Compatibility (ADR 0021)

Behaviour that would break an existing script is dormant in 1.4.x and becomes the default at v1.5.0. Opt in early with NSELF_V15=1 (Compat-V15).

Case	v1.4 mode (default in 1.4.x)	v1.5 mode (NSELF_V15=1)
--json on a none command that had no --json before (for example restart)	E402, exit 1 (it was an unknown-flag error)	same
--json on a none command whose own json flag was accepted and ignored (for example config validate)	unchanged: accepted and ignored	E402, exit 1
Unknown flag or bad arguments	cobra's message, unchanged	coded E401; values you typed (for example after -x… or a secret-named flag) are removed from the message

Schemas

Every JSON contract is published as a JSON Schema (draft 2020-12) under schemas/ in the repository. The files are generated from the Go types by tools/schemagen; never edit one by hand. make schemas regenerates them and make schemas-check (also go run ./tools/schemagen -check) fails when a committed file is stale.

File	Describes
schemas/envelope.v1.schema.json	The envelope: exactly one of data or error, schema_version "1", optional meta (deprecations[] with old, new, removal_at; warnings[])
schemas/error.v1.schema.json	The error object: code (E and three digits), message, optional cause, remediation, docs_url, exit_code, class
schemas/command-registry.v1.schema.json	The command registry document (nself help --json data and .github/command-registry.json)
schemas/commands/<command>.v1.schema.json	The data of one envelope command; the path is the command with spaces as - (help today)
schemas/index.json	Every generated schema with its $id

Each schema has the $id urn:nself:cli:schema:<name>:v1. The envelope refers to the error schema by that $id, so a validator needs error.v1 loaded alongside envelope.v1 (the repository tests resolve it from schemas/index.json). Any 2020-12 validator works. To check a command's data with check-jsonschema:

nself help --json | jq .data > data.json
check-jsonschema --schemafile schemas/commands/help.v1.schema.json data.json

A breaking change to a schema needs a new v2 file, not an edit of v1. Golden fixtures for every envelope command live in cmd/commands/testdata/json/; the contract test validates each against its schema and round-trips it through the Go type.

Coming in v1.5

These are part of the design but not shipped yet; the pages and flags below do not exist in 1.4.x.

• The v1 envelope on stdout: {"schema_version":"1","command":"<path>","data":…} for success, "error":… instead of data on failure, with stdout carrying exactly one JSON document. It lands with P7-REG-06 (error envelope, exit classes), P7-REG-07 (nself help --json) and P7-REG-09 (status, doctor, config pilots). Until then a refused or failed --json command prints text on stderr only.
• NSELF_JSON_LEGACY=1 (or true): once the envelope is the default in v1.5 mode, it restores the old bare JSON of status, doctor and config show --format json for one minor release, with a one-line warning on stderr. Removed in v1.6.0.
• The command registry (.github/command-registry.json, published by nself help --json) listing the JSON support of every command; its own page lands with P7-REG-07. Today nself help --json is refused like any other none command.

See also

• error-codes for E401 (invalid usage) and E402 (JSON output not supported).