Enable running tests without default features

Currently various features fail to build when enabled without default
features. This is because many tests need feature gating.

Feature gating the import statements quickly turns into spaghetti when
trying to cover all combinations of two features correctly, instead just
allow unused imports on `tests` modules where needed.

Add correct feature requirements to the examples so they also can be run
without default features.

Improve the CI script by adding `std` and `alloc` to the feature matrix.
Add `--no-default-features` to test runs in the CI script.

Cargo.toml

@@ -49,14 +49,15 @@ rand = { version = "0.6", features = ["wasm-bindgen"] }
 
 [[example]]
 name = "sign_verify_recovery"
-required-features = ["recovery"]
+required-features = ["alloc", "recovery"]
 
 [[example]]
 name = "sign_verify"
+required-features = ["alloc"]
 
 [[example]]
 name = "generate_keys"
-required-features = ["rand"]
+required-features = ["alloc", "rand"]
 
 [workspace]
 members = ["secp256k1-sys"]

contrib/test.sh

@@ -1,6 +1,7 @@
 #!/bin/sh -ex
 
-FEATURES="bitcoin_hashes global-context lowmemory rand rand-std recovery serde"
+# TODO: Add "alloc" once we bump MSRV to past 1.29
+FEATURES="bitcoin_hashes global-context lowmemory rand rand-std recovery serde std"
 
 # Use toolchain if explicitly specified
 if [ -n "$TOOLCHAIN" ]
@@ -20,17 +21,16 @@ cargo test --all
 
 if [ "$DO_FEATURE_MATRIX" = true ]; then
     cargo build --all --no-default-features
-    #This doesn't work but probably should --andrew
-    #cargo test --all --no-default-features
+    cargo test --all --no-default-features
 
     # All features
     cargo build --all --no-default-features --features="$FEATURES"
-    cargo test --all --features="$FEATURES"
+    cargo test --all --no-default-features --features="$FEATURES"
     # Single features
     for feature in ${FEATURES}
     do
         cargo build --all --no-default-features --features="$feature"
-        cargo test --all --features="$feature"
+        cargo test --all --no-default-features --features="$feature"
     done
 
     # Other combos 
@@ -45,9 +45,9 @@ if [ "$DO_FEATURE_MATRIX" = true ]; then
     fi
 
     # Examples
-    cargo run --example sign_verify
-    cargo run --example sign_verify_recovery --features=recovery
-    cargo run --example generate_keys --features=rand
+    cargo run --example sign_verify --features=alloc
+    cargo run --example sign_verify_recovery --features=recovery,alloc
+    cargo run --example generate_keys --features=rand,alloc
 fi
 
 # Docs

src/context.rs

@@ -9,7 +9,7 @@ use Secp256k1;
 #[cfg_attr(docsrs, doc(cfg(any(feature = "std", feature = "alloc"))))]
 pub use self::alloc_only::*;
 
-#[cfg(feature = "global-context-less-secure")]
+#[cfg(all(feature = "global-context-less-secure", feature = "std"))]
 #[cfg_attr(docsrs, doc(cfg(any(feature = "global-context", feature = "global-context-less-secure"))))]
 /// Module implementing a singleton pattern for a global `Secp256k1` context
 pub mod global {
@@ -35,6 +35,7 @@ pub mod global {
     impl Deref for GlobalContext {
         type Target = Secp256k1<All>;
 
+        #[allow(unused_mut)]    // Unused when "global-context" is not enabled.
         fn deref(&self) -> &Self::Target {
             static ONCE: Once = Once::new();
             static mut CONTEXT: Option<Secp256k1<All>> = None;

src/ecdh.rs

@@ -127,6 +127,7 @@ impl SharedSecret {
     /// `SharedSecret` can be easily created via the `From` impl from arrays.
     /// # Examples
     /// ```
+    /// # #[cfg(any(feature = "alloc", features = "std"))] {
     /// # use secp256k1::ecdh::SharedSecret;
     /// # use secp256k1::{Secp256k1, PublicKey, SecretKey};
     /// # fn sha2(_a: &[u8], _b: &[u8]) -> [u8; 32] {[0u8; 32]}
@@ -139,7 +140,7 @@ impl SharedSecret {
     ///     let hash: [u8; 32] = sha2(&x,&y);
     ///     hash.into()
     /// });
-    ///
+    /// # }
     /// ```
     pub fn new_with_hash<F>(point: &PublicKey, scalar: &SecretKey, mut hash_function: F) -> SharedSecret
         where F: FnMut([u8; 32], [u8; 32]) -> SharedSecret {
@@ -170,13 +171,16 @@ impl SharedSecret {
 #[cfg(test)]
 mod tests {
     use super::*;
+    #[cfg(any(feature = "alloc", feature = "std"))]
     use rand::thread_rng;
-    use super::super::Secp256k1;
+    #[cfg(any(feature = "alloc", feature = "std"))]
+    use Secp256k1;
 
     #[cfg(target_arch = "wasm32")]
     use wasm_bindgen_test::wasm_bindgen_test as test;
 
     #[test]
+    #[cfg(any(feature = "alloc", feature = "std"))]
     fn ecdh() {
         let s = Secp256k1::signing_only();
         let (sk1, pk1) = s.generate_keypair(&mut thread_rng());
@@ -190,6 +194,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(any(feature = "alloc", feature = "std"))]
     fn ecdh_with_hash() {
         let s = Secp256k1::signing_only();
         let (sk1, pk1) = s.generate_keypair(&mut thread_rng());
@@ -203,6 +208,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(any(feature = "alloc", feature = "std"))]
     fn ecdh_with_hash_callback() {
         let s = Secp256k1::signing_only();
         let (sk1, pk1) = s.generate_keypair(&mut thread_rng());

src/ecdsa/mod.rs

@@ -431,7 +431,7 @@ impl<C: Verification> Secp256k1<C> {
     /// verify-capable context.
     ///
     /// ```rust
-    /// # #[cfg(feature="rand")] {
+    /// # #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))] {
     /// # use secp256k1::rand::rngs::OsRng;
     /// # use secp256k1::{Secp256k1, Message, Error};
     /// #
@@ -460,7 +460,7 @@ impl<C: Verification> Secp256k1<C> {
     /// verify-capable context.
     ///
     /// ```rust
-    /// # #[cfg(feature="rand")] {
+    /// # #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))] {
     /// # use secp256k1::rand::rngs::OsRng;
     /// # use secp256k1::{Secp256k1, Message, Error};
     /// #

src/ecdsa/recovery.rs

@@ -201,6 +201,7 @@ impl<C: Verification> Secp256k1<C> {
 
 
 #[cfg(test)]
+#[allow(unused_imports)]
 mod tests {
     use super::*;
     use rand::{RngCore, thread_rng};
@@ -210,6 +211,7 @@ mod tests {
     use wasm_bindgen_test::wasm_bindgen_test as test;
 
     #[test]
+    #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))]
     fn capabilities() {
         let sign = Secp256k1::signing_only();
         let vrfy = Secp256k1::verification_only();
@@ -243,6 +245,7 @@ mod tests {
 
     #[test]
     #[cfg(not(fuzzing))]  // fixed sig vectors can't work with fuzz-sigs
+    #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))]
     fn sign() {
         let mut s = Secp256k1::new();
         s.randomize(&mut thread_rng());
@@ -266,6 +269,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))]
     fn sign_and_verify_fail() {
         let mut s = Secp256k1::new();
         s.randomize(&mut thread_rng());
@@ -289,6 +293,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))]
     fn sign_with_recovery() {
         let mut s = Secp256k1::new();
         s.randomize(&mut thread_rng());
@@ -305,6 +310,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(all(feature="rand-std", any(feature = "alloc", feature = "std")))]
     fn bad_recovery() {
         let mut s = Secp256k1::new();
         s.randomize(&mut thread_rng());