[review] make features additive

pretty_assertions/Cargo.toml

@@ -32,5 +32,11 @@ output_vt100 = "0.1.2"
 ctor = "0.1.9"
 
 [features]
-default = []
-no_std = []
+default = ["std"]
+
+# Use the Rust standard library.
+# Exactly one of `std` and `alloc` is required.
+std = []
+# Use the `alloc` crate.
+# Exactly one of `std` and `alloc` is required.
+alloc = []

pretty_assertions/src/lib.rs

@@ -65,15 +65,19 @@
 //!
 //! ## Features
 //!
-//! Features provided by the crate are as follows:
+//! Features provided by the crate are:
 //!
+//! - `std`: Use the Rust standard library. Enabled by default.
+//!   Exactly one of `std` and `alloc` is required.
+//! - `alloc`: Use the `alloc` crate.
+//!   Exactly one of `std` and `alloc` is required.
 //! - `unstable`: opt-in to unstable features that may not follow Semantic Versioning.
 //!   Implmenetion behind this feature is subject to change without warning between patch versions.
 
-#![cfg_attr(feature = "no_std", no_std)]
+#![cfg_attr(not(feature = "std"), no_std)]
 #![deny(clippy::all, missing_docs, unsafe_code)]
 
-#[cfg(feature = "no_std")]
+#[cfg(feature = "alloc")]
 #[macro_use]
 extern crate alloc;
 pub use ansi_term::Style;

pretty_assertions/src/printer.rs

@@ -1,3 +1,5 @@
+#[cfg(feature = "alloc")]
+use alloc::format;
 use ansi_term::{
     Colour::{Fixed, Green, Red},
     Style,
@@ -210,7 +212,7 @@ fn write_inline_diff<TWrite: fmt::Write>(f: &mut TWrite, left: &str, right: &str
 mod test {
     use super::*;
 
-    #[cfg(feature = "no_std")]
+    #[cfg(feature = "alloc")]
     use alloc::string::String;
 
     // ANSI terminal codes used in our outputs.
@@ -233,8 +235,8 @@ mod test {
         let mut actual = String::new();
         printer(&mut actual, left, right).expect("printer function failed");
 
-        // Cannot use IO with no_std
-        #[cfg(not(feature = "no_std"))]
+        // Cannot use IO without stdlib
+        #[cfg(feature = "std")]
         println!(
             "## left ##\n\
              {}\n\

pretty_assertions/tests/macros.rs

@@ -1,14 +1,14 @@
-#![cfg_attr(feature = "no_std", no_std)]
+#![cfg_attr(not(feature = "std"), no_std)]
 #![no_implicit_prelude]
 
-#[cfg(feature = "no_std")]
+#[cfg(feature = "alloc")]
 extern crate alloc;
 
 #[allow(clippy::eq_op)]
 mod assert_eq {
-    #[cfg(feature = "no_std")]
+    #[cfg(feature = "alloc")]
     use ::alloc::string::{String, ToString};
-    #[cfg(not(feature = "no_std"))]
+    #[cfg(feature = "std")]
     use ::std::string::{String, ToString};
 
     #[test]
@@ -100,9 +100,9 @@ mod assert_eq {
 }
 
 mod assert_ne {
-    #[cfg(feature = "no_std")]
+    #[cfg(feature = "alloc")]
     use ::alloc::string::{String, ToString};
-    #[cfg(not(feature = "no_std"))]
+    #[cfg(feature = "std")]
     use ::std::string::{String, ToString};
 
     #[test]

scripts/check

@@ -15,10 +15,19 @@ cargo audit --deny warnings
 eprintln "Linting sources"
 cargo clippy --all-targets -- -D warnings
 
-eprintln "Running tests"
+# We cd to package directory as it's the only one with tests
+# and cargo doesn't support feature flags in virtual workspaces
+# https://github.com/rust-lang/cargo/issues/5364
+pushd pretty_assertions
+
+eprintln "Running tests (default)"
 cargo test
-eprintln "Running tests (no_std)"
-cargo test --features no_std
+eprintln "Running tests (std)"
+cargo test --no-default-features --features std
+eprintln "Running tests (alloc)"
+cargo test --no-default-features --features alloc
+
+popd
 
 eprintln "Running unit tests (unstable)"
 cargo +nightly test --manifest-path pretty_assertions/Cargo.toml --all --features unstable