Initial no_std support

Since `core::error` isn't in Rust until 1.81, we can't use it and
so we only derive `Error` for the error types when building with
the `std` feature.

Also, `webdriver` implies `std` as well (for now?).

Author: waywardmonkeys

Cargo.toml

@@ -11,11 +11,12 @@ edition = "2021"
 rust-version = "1.61"
 
 [features]
-default = ["serde", "webdriver"]
+default = ["serde", "std", "webdriver"]
 serde = ["dep:serde", "bitflags/serde"]
-webdriver = ["unicode-segmentation"]
+std = ["serde?/std"]
+webdriver = ["std", "unicode-segmentation"]
 
 [dependencies]
 bitflags = "2"
-serde = { version = "1.0.0", optional = true, features = ["derive"] }
+serde = { version = "1.0.0", optional = true, default-features = false, features = ["derive"] }
 unicode-segmentation = { version = "1.2.0", optional = true }

convert.py

@@ -92,8 +92,10 @@ def convert_key(text, file):
 #![cfg_attr(rustfmt, rustfmt_skip)]
 #![allow(clippy::doc_markdown)]
 
-use std::fmt::{self, Display};
-use std::str::FromStr;
+use alloc::string::{String, ToString};
+use core::fmt::{self, Display};
+use core::str::FromStr;
+#[cfg(feature = "std")]
 use std::error::Error;
 
 /// Key represents the meaning of a keypress.
@@ -159,6 +161,7 @@ def convert_key(text, file):
     }
 }
 
+#[cfg(feature = "std")]
 impl Error for UnrecognizedKeyError {}
 
 /// Check if string can be used as a `Key::Character` _keystring_.
@@ -189,8 +192,9 @@ def convert_code(text, file):
 #![cfg_attr(rustfmt, rustfmt_skip)]
 #![allow(clippy::doc_markdown)]
 
-use std::fmt::{self, Display};
-use std::str::FromStr;
+use core::fmt::{self, Display};
+use core::str::FromStr;
+#[cfg(feature = "std")]
 use std::error::Error;
 
 /// Code is the physical position of a key.
@@ -294,6 +298,7 @@ def convert_code(text, file):
     }
 }
 
+#[cfg(feature = "std")]
 impl Error for UnrecognizedCodeError {}
     """, file=file)
 

src/code.rs

@@ -3,8 +3,9 @@
 #![cfg_attr(rustfmt, rustfmt_skip)]
 #![allow(clippy::doc_markdown)]
 
-use std::fmt::{self, Display};
-use std::str::FromStr;
+use core::fmt::{self, Display};
+use core::str::FromStr;
+#[cfg(feature = "std")]
 use std::error::Error;
 
 /// Code is the physical position of a key.
@@ -931,5 +932,6 @@ impl fmt::Display for UnrecognizedCodeError {
     }
 }
 
+#[cfg(feature = "std")]
 impl Error for UnrecognizedCodeError {}
 

src/key.rs

@@ -3,8 +3,10 @@
 #![cfg_attr(rustfmt, rustfmt_skip)]
 #![allow(clippy::doc_markdown)]
 
-use std::fmt::{self, Display};
-use std::str::FromStr;
+use alloc::string::{String, ToString};
+use core::fmt::{self, Display};
+use core::str::FromStr;
+#[cfg(feature = "std")]
 use std::error::Error;
 
 /// Key represents the meaning of a keypress.
@@ -1316,6 +1318,7 @@ impl fmt::Display for UnrecognizedKeyError {
     }
 }
 
+#[cfg(feature = "std")]
 impl Error for UnrecognizedKeyError {}
 
 /// Check if string can be used as a `Key::Character` _keystring_.

src/lib.rs

@@ -5,8 +5,12 @@
 //! input in a cross-platform way.
 
 #![warn(clippy::doc_markdown)]
+#![cfg_attr(all(not(feature = "std"), not(test)), no_std)]
 
-use std::fmt;
+extern crate alloc;
+
+use alloc::string::String;
+use core::fmt;
 
 pub use crate::code::{Code, UnrecognizedCodeError};
 pub use crate::key::{Key, UnrecognizedKeyError};