Interpret an env var as boolean false iff it is unset

If it is set to any value, including "" (and of course "false") then
it is true.

This matches the semantics which clap seems likely to adopt:
https://github.com/clap-rs/clap/issues/1476#issuecomment-652344026

1 files changed, 2 insertions, 6 deletions

diff --git a/src/env.rs b/src/env.rs
index dc30ecc..0a988f9 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -9,11 +9,7 @@ pub fn get_env_var(name: &str) -> Option<String> {
     }
 }
 
+/// If `name` is set to any value at all (including "") then return true; else false.
 pub fn get_boolean_env_var(name: &str) -> bool {
-    let val = get_env_var(name).map(|s| s.to_lowercase());
-    match val.as_deref() {
-        None => false,
-        Some("false") => false,
-        Some(_) => true,
-    }
+    env::var(name).ok().is_some()
 }