Module env_flag 

Shared truthiness parsing for boolean-ish environment-variable flags. Shared truthiness parsing for environment-variable flags.

Two flags in this crate read boolean-ish env vars — MINIEXTENDR_BACKTRACE (backtrace.rs) and _R_CHECK_LIMIT_CORES_ (optionals/parallel.rs) — and they used to disagree on what counts as “on” (true/1 vs. anything but false). parse_bool is the single source of truth, deliberately aligned with R’s own config_val_to_logical (tools/R/utils.R): a case-insensitive, whitespace-trimmed match against explicit truthy/falsy sets.

Recognized values (case-insensitive, surrounding whitespace trimmed):

• truthy: yes, true, 1, on
• falsy: no, false, 0, off, `` (empty)

Anything else is unrecognized (None) — the caller supplies the default, so each flag keeps control of its own “garbage” policy (see the two call sites for their deliberately different defaults).

Functions

parse_bool 🔒

Parse an environment-flag value as a boolean, using R’s config_val_to_logical rules (see module docs). Returns None for values outside the recognized truthy/falsy sets so the caller picks the default.