Support no_std integration tests

Cargo.toml

@@ -34,11 +34,7 @@ default = ["std", "perf", "unicode", "regex-syntax/default"]
 
 # ECOSYSTEM FEATURES
 
-# The 'std' feature permits the regex crate to use the standard library. This
-# is intended to support future use cases where the regex crate may be able
-# to compile without std, and instead just rely on 'core' and 'alloc' (for
-# example). Currently, this isn't supported, and removing the 'std' feature
-# will prevent regex from compiling.
+# The 'std' feature permits the regex crate to use the standard library.
 std = [
   "aho-corasick?/std",
   "memchr?/std",

test

@@ -13,15 +13,11 @@ cd "$(dirname "$0")"
 echo "===== DEFAULT FEATURES ====="
 cargo test
 
-# no-std mode is annoyingly difficult to test. Currently, the integration tests
-# don't run. So for now, we just test that library tests run. (There aren't
-# many because `regex` is just a wrapper crate.)
-cargo test --no-default-features --lib
-
 echo "===== DOC TESTS ====="
 cargo test --doc
 
 features=(
+    ""
     "std"
     "std unicode"
     "std unicode-perl"
@@ -36,7 +32,7 @@ features=(
 )
 for f in "${features[@]}"; do
     echo "===== FEATURE: $f ====="
-    cargo test --test integration --no-default-features --features "$f"
+    cargo test --test integration --no-default-features --features="$f"
 done
 
 # And test the probably-forever-nightly-only 'pattern' feature...

tests/lib.rs

@@ -16,6 +16,18 @@ const BLACKLIST: &[&str] = &[
     // Nothing to blacklist yet!
 ];
 
+#[cfg(not(feature = "std"))]
+pub(crate) fn nostd_compat<T: core::fmt::Debug>(
+    re: Result<T, regex::Error>,
+) -> T {
+    assert!(
+        re.is_ok(),
+        "regex compilation failed: {}",
+        re.as_ref().unwrap_err(),
+    );
+    re.unwrap()
+}
+
 fn suite() -> anyhow::Result<regex_test::RegexTests> {
     let _ = env_logger::try_init();
 

tests/suite_bytes.rs

@@ -1,3 +1,5 @@
+#[cfg(not(feature = "std"))]
+use crate::nostd_compat;
 use {
     anyhow::Result,
     regex::bytes::{Regex, RegexBuilder},
@@ -90,7 +92,11 @@ fn compiler(
         .case_insensitive(test.case_insensitive())
         .unicode(test.unicode())
         .line_terminator(test.line_terminator())
-        .build()?;
+        .build();
+    #[cfg(not(feature = "std"))]
+    let re = nostd_compat(re);
+    #[cfg(feature = "std")]
+    let re = re?; // Propagate any errors.
     Ok(CompiledRegex::compiled(move |test| run_test(&re, test)))
 }
 

tests/suite_bytes_set.rs

@@ -1,3 +1,5 @@
+#[cfg(not(feature = "std"))]
+use crate::nostd_compat;
 use {
     anyhow::Result,
     regex::bytes::{RegexSet, RegexSetBuilder},
@@ -66,6 +68,10 @@ fn compiler(
         .case_insensitive(test.case_insensitive())
         .unicode(test.unicode())
         .line_terminator(test.line_terminator())
-        .build()?;
+        .build();
+    #[cfg(not(feature = "std"))]
+    let re = nostd_compat(re);
+    #[cfg(feature = "std")]
+    let re = re?; // Propagate any errors.
     Ok(CompiledRegex::compiled(move |test| run_test(&re, test)))
 }

tests/suite_string.rs

@@ -1,3 +1,5 @@
+#[cfg(not(feature = "std"))]
+use crate::nostd_compat;
 use {
     anyhow::Result,
     regex::{Regex, RegexBuilder},
@@ -98,7 +100,11 @@ fn compiler(
         .case_insensitive(test.case_insensitive())
         .unicode(test.unicode())
         .line_terminator(test.line_terminator())
-        .build()?;
+        .build();
+    #[cfg(not(feature = "std"))]
+    let re = nostd_compat(re);
+    #[cfg(feature = "std")]
+    let re = re?; // Propagate any errors.
     Ok(CompiledRegex::compiled(move |test| run_test(&re, test)))
 }
 

tests/suite_string_set.rs

@@ -1,3 +1,5 @@
+#[cfg(not(feature = "std"))]
+use crate::nostd_compat;
 use {
     anyhow::Result,
     regex::{RegexSet, RegexSetBuilder},
@@ -74,6 +76,10 @@ fn compiler(
         .case_insensitive(test.case_insensitive())
         .unicode(test.unicode())
         .line_terminator(test.line_terminator())
-        .build()?;
+        .build();
+    #[cfg(not(feature = "std"))]
+    let re = nostd_compat(re);
+    #[cfg(feature = "std")]
+    let re = re?; // Propagate any errors.
     Ok(CompiledRegex::compiled(move |test| run_test(&re, test)))
 }