feat(env_filter): make the regex feature compatible with no_std

Author: cagatay-y

.github/workflows/ci.yml

@@ -76,9 +76,8 @@ jobs:
         - cargo hack check --each-feature --locked --rust-version --ignore-private --package env_logger --all-targets --keep-going
         # When the std feature is enabled, a lower MSRV of 1.71 is sufficient and was the MSRV for the crate before std was made optional.
         # To make sure we keep it that way, check configurations with std enabled and disabled separately and with their respective MSRVs.
-        # "--at-least-one-of" requires "--feature-powerset", which can be made to emulate "--each-feature" with "--depth 1".
-        - cargo hack check --feature-powerset --depth 1 --locked --version-range 1.71..=1.71 --ignore-private --package env_filter --all-targets --keep-going --at-least-one-of std,default,regex
-        - cargo hack check --no-default-features --locked --version-range 1.81..=1.81 --ignore-private --package env_filter --all-targets --keep-going
+        - cargo hack check --feature-powerset --depth 2 --locked --version-range 1.71..=1.71 --ignore-private --package env_filter --all-targets --keep-going --at-least-one-of std,default
+        - cargo hack check --each-feature --locked --version-range 1.81..=1.81 --ignore-private --package env_filter --all-targets --keep-going --exclude-features std,default
   minimal-versions:
     name: Minimal versions
     strategy:

crates/env_filter/Cargo.toml

@@ -26,12 +26,12 @@ pre-release-replacements = [
 
 [features]
 default = ["std", "regex"]
-regex = ["std", "dep:regex"]
-std = []
+regex = ["dep:regex"]
+std = ["regex/std"]
 
 [dependencies]
 log = { version = "0.4.29", default-features = false }
-regex = { version = "1.12.3", optional = true, default-features=false, features=["std", "perf"] }
+regex = { version = "1.12.3", optional = true, default-features=false, features=["perf"] }
 
 [dev-dependencies]
 snapbox = "1.0"