truthy¶

What this rule does¶

Reports bareword string values that YAML 1.1 would interpret as booleans. By default only true and false are accepted; all other YAML 1.1 truthy words (yes, no, on, off, True, Yes, ...) are flagged.

Why this matters¶

Silent type coercion. A literal yes parses as the boolean true under YAML 1.1, which is rarely what an author intended for a country code, a country name, or a configuration value.
Cross-parser drift. Some libraries still default to YAML 1.1 semantics, others to 1.2; flagging the ambiguous words makes the document behave the same way everywhere.

Configuration¶

[rules.truthy]
level = "error"
allowed-values = ["true", "false"]
check-keys = true

Option	Default	Description
`allowed-values`	`["true", "false"]`	Bareword values that are permitted. Everything else triggers the rule.
`check-keys`	`true`	Also report truthy values used as mapping keys.

GitHub Actions workflows¶

A workflow's required on: key is a truthy bareword, so truthy reports it:

$ ryl check .github/workflows/ci.yml
.github/workflows/ci.yml
  2:1       error    truthy value should be one of [false, true]  (truthy)

Quoting the key does not help. ryl resolves the YAML 1.2 core schema, where on is an ordinary string, so 'on': then trips quoted-strings under required: only-when-needed. yamllint accepts the quotes because PyYAML reads on as a YAML 1.1 boolean — see YAML version compatibility.

Three ways to settle it, narrowest first:

Approach	Effect
`per-file-ignores` on the workflow directory	`truthy` still runs everywhere else. Recommended
`check-keys = false`	No key is checked, in any file
`on` in `allowed-values`	Also permits `on` as a value, in any file

The recommended form scopes the exemption to the files that need it:

[rules.truthy]

[per-file-ignores]
".github/workflows/*" = ["truthy"]

Both alternatives are global, which is the trade-off to weigh: they are simpler to write, and they stop truthy catching an accidental enabled: yes in the same repo.

Examples¶

Allowed (defaults)¶

enabled: true
visible: false

Reported (defaults)¶

enabled: yes
flag: On
country: NO
debug: True

After `ryl check --fix` (defaults)¶

enabled: yes
flag: On
country: NO
debug: true

Allowed (with `allowed-values: ["true", "false", "yes", "no"]`)¶

enabled: yes
visible: no

YAML version directive¶

The rule honours an explicit %YAML directive: under %YAML 1.2 the barewords resolve to plain strings, so only true/false spellings are flagged; under %YAML 1.1 (or no directive) the full 1.1 truthy word list is flagged.

Automatic fixing¶

ryl check --fix rewrites a flagged case variant of true or false (True, TRUE, False, FALSE) to the first spelling of the same boolean that allowed-values permits, trying lowercase, then title case, then upper case. Every one of those spellings is the same boolean under YAML 1.1 and 1.2, so the value does not change. When allowed-values has no spelling of that boolean, the value is left as it is.

The fix is partial: yes, no, on, off and their case variants are never rewritten, because the right replacement (quote it to keep the string, or change it to a boolean) depends on what the author meant.

With check-keys on, keys are fixed too. That can surface a duplicate key: True: 1 and true: 2 in one mapping were always the same boolean key, and key-duplicates reports it once both read true.

quoted-strings — quoting a value disables type coercion so the literal stays a string.
empty-values — a related class of "what did the author actually mean" ambiguity.