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//! Realia provides attribute macros for conditional compilation, //! analogous to `#[cfg(...)]` and `#[cfg_attr(...)]`. #![allow(clippy::needless_doctest_main)] extern crate proc_macro; mod attr; mod dep; mod expr; mod metadata; use crate::attr::Then; use crate::expr::Expr; use proc_macro::TokenStream; use proc_macro2::{Ident, Span, TokenStream as TokenStream2}; use quote::quote; use syn::{parse_macro_input, ItemFn, Result}; /// Checks whether an environment variable is defined and optionally /// what value it has. /// /// If you use this attribute, your project should include a `build.rs` that /// triggers a rebuild when any environment variables of interest change: /// /// ``` /// fn main() { /// // Necessary when using #[realia::env("FOO")] /// println!("cargo:rerun-if-env-changed=FOO"); /// } /// ``` /// /// # Example /// ``` /// #[realia::env("CI")] /// fn example() { /// println!("CI is defined"); /// } /// ``` /// /// ``` /// #[realia::env("CI", "true")] /// fn example() { /// println!("CI is set to true"); /// } /// ``` #[proc_macro_attribute] pub fn env(args: TokenStream, input: TokenStream) -> TokenStream { cfg("env", args, input) } /// Checks whether an executable exists on the `PATH`. /// /// If you use this attribute, your project should include a `build.rs` that /// triggers a rebuild when the `PATH` environment variable changes: /// /// ``` /// fn main() { /// println!("cargo:rerun-if-env-changed=PATH"); /// } /// ``` /// /// # Example /// ``` /// #[realia::cmd("git")] /// fn example() { /// println!("Git is installed and available"); /// } /// ``` #[proc_macro_attribute] pub fn cmd(args: TokenStream, input: TokenStream) -> TokenStream { cfg("cmd", args, input) } /// Checks whether a crate has a certain dependency and optionally if that /// dependency is a certain version. /// /// The first argument is an "anchor crate", which should generally be your crate. /// Since this functionality is implemented by checking the output of /// `cargo metadata --manifest-path $CARGO_MANIFEST_DIR/Cargo.toml`, /// the anchor is used to ensure consistent results when `$CARGO_MANIFEST_DIR` /// changes (e.g., when building your crate directly vs when building a downstream crate). /// /// This accounts for target-specific dependencies, but currently ignores any /// optional dependencies enabled by features. /// /// # Example /// ``` /// #[realia::dep("realia", "syn")] /// fn example() { /// println!("Realia depends on Syn"); /// } /// ``` /// /// ``` /// #[realia::dep("realia", "syn", "1.0.34")] /// fn example() { /// println!("Realia uses Syn 1.0.34 exactly"); /// } /// ``` #[proc_macro_attribute] pub fn dep(args: TokenStream, input: TokenStream) -> TokenStream { cfg("dep", args, input) } /// Checks whether a crate has a certain dependency at or above a certain version. /// /// The first argument is an "anchor crate", which should generally be your crate. /// Since this functionality is implemented by checking the output of /// `cargo metadata --manifest-path $CARGO_MANIFEST_DIR/Cargo.toml`, /// the anchor is used to ensure consistent results when `$CARGO_MANIFEST_DIR` /// changes (e.g., when building your crate directly vs when building a downstream crate). /// /// This accounts for target-specific dependencies, but currently ignores any /// optional dependencies enabled by features. /// /// # Example /// ``` /// #[realia::dep_since("realia", "syn", "1.0.34")] /// fn example() { /// println!("Realia uses Syn 1.0.34 or newer"); /// } /// ``` #[proc_macro_attribute] pub fn dep_since(args: TokenStream, input: TokenStream) -> TokenStream { cfg("dep_since", args, input) } /// Checks whether a crate has a certain dependency below a certain version. /// /// The first argument is an "anchor crate", which should generally be your crate. /// Since this functionality is implemented by checking the output of /// `cargo metadata --manifest-path $CARGO_MANIFEST_DIR/Cargo.toml`, /// the anchor is used to ensure consistent results when `$CARGO_MANIFEST_DIR` /// changes (e.g., when building your crate directly vs when building a downstream crate). /// /// This accounts for target-specific dependencies, but currently ignores any /// optional dependencies enabled by features. /// /// # Example /// ``` /// #[realia::dep_before("realia", "syn", "1.0.34")] /// fn example() { /// println!("Realia uses Syn 1.0.33 or older"); /// } /// ``` #[proc_macro_attribute] pub fn dep_before(args: TokenStream, input: TokenStream) -> TokenStream { cfg("dep_before", args, input) } /// Checks whether a crate has a certain dependency installed from the registry /// (as opposed to being a Git dependency or a path dependency). This is useful /// if you have non-registry dependencies with a /// [registry fallback for publishing](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#multiple-locations). /// /// The first argument is an "anchor crate", which should generally be your crate. /// Since this functionality is implemented by checking the output of /// `cargo metadata --manifest-path $CARGO_MANIFEST_DIR/Cargo.toml`, /// the anchor is used to ensure consistent results when `$CARGO_MANIFEST_DIR` /// changes (e.g., when building your crate directly vs when building a downstream crate). /// /// This accounts for target-specific dependencies, but currently ignores any /// optional dependencies enabled by features. /// /// # Example /// ``` /// #[realia::dep_from_registry("realia", "syn")] /// fn example() { /// println!("Realia uses Syn from the registry"); /// } /// ``` #[proc_macro_attribute] pub fn dep_from_registry(args: TokenStream, input: TokenStream) -> TokenStream { cfg("dep_from_registry", args, input) } /// Inverts another condition. /// /// # Example /// ``` /// #[realia::not(cmd("git"))] /// fn example() { /// println!("Git is not installed"); /// } /// ``` #[proc_macro_attribute] pub fn not(args: TokenStream, input: TokenStream) -> TokenStream { cfg("not", args, input) } /// Checks if at least one of multiple conditions is met. /// /// # Example /// ``` /// #[realia::any(cmd("git"), cmd("hg"))] /// fn example() { /// println!("Some version control is available"); /// } /// ``` #[proc_macro_attribute] pub fn any(args: TokenStream, input: TokenStream) -> TokenStream { cfg("any", args, input) } /// Checks if multiple conditions are met. /// /// # Example /// ``` /// #[realia::all(cmd("git"), env("GIT_AUTHOR_NAME"))] /// fn example() { /// println!("Git is available and GIT_AUTHOR_NAME is defined"); /// } /// ``` #[proc_macro_attribute] pub fn all(args: TokenStream, input: TokenStream) -> TokenStream { cfg("all", args, input) } fn cfg(top: &str, args: TokenStream, input: TokenStream) -> TokenStream { match try_cfg(top, args, input) { Ok(tokens) => tokens, Err(err) => TokenStream::from(err.to_compile_error()), } } fn try_cfg(top: &str, args: TokenStream, input: TokenStream) -> Result<TokenStream> { let args = TokenStream2::from(args); let top = Ident::new(top, Span::call_site()); let mut full_args = quote!(#top); if !args.is_empty() { full_args.extend(quote!((#args))); } let expr: Expr = syn::parse2(full_args)?; if expr.eval() { Ok(input) } else { Ok(TokenStream::new()) } } /// Applies an attribute when the condition is met. /// You can also specify `const` this way. /// /// # Example /// ``` /// #[test] /// #[realia::attr(not(cmd("git")), ignore)] /// fn some_test_that_requires_git() {} /// ``` /// /// ``` /// #[realia::attr(env("USE_CONST_FN"), const)] /// fn this_becomes_const() {} /// ``` #[proc_macro_attribute] pub fn attr(args: TokenStream, input: TokenStream) -> TokenStream { let args = parse_macro_input!(args as attr::Args); match try_attr(args, input) { Ok(tokens) => tokens, Err(err) => TokenStream::from(err.to_compile_error()), } } fn try_attr(args: attr::Args, input: TokenStream) -> Result<TokenStream> { if !args.condition.eval() { return Ok(input); } match args.then { Then::Const(const_token) => { let mut input: ItemFn = syn::parse(input)?; input.sig.constness = Some(const_token); Ok(TokenStream::from(quote!(#input))) } Then::Attribute(then) => { let input = TokenStream2::from(input); Ok(TokenStream::from(quote! { #[cfg_attr(all(), #then)] #input })) } } }