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// Copyright 2018 oooutlk@outlook.com. See the COPYRIGHT // file at the top-level directory of this distribution. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! # Problem To Solve //! //! Sometimes a crate needs to gather information from its downstream users. //! //! Frequently used mechanisms: //! //! - Cargo Features. //! //! The are friendly to cargo tools but not applicable for passing free contents //! because they are predefined options. //! //! - Environment Variables. //! //! They can pass free contents, but are not friendly to cargo tools. //! //! # Project Goal //! //! To provide a mechanism that is both friendly to cargo tools and able to pass //! free contents. //! //! # Library Overview //! //! This library helps to send metadata through the hierarchy of crates, from //! downstream crates to one of their common ancestor. //! //! The main API is `inwelling()`, which is expected to be called in `build.rs` of //! the common ancestor crate. //! //! ```text //! . +--------------> [topmost crate] //! . | 3 | ^ //! . | 4| |8 //! . | | | //! . | [dependencies] //! . |2 | | //! . | | | //! . | (metadata) |5 7| (API) //! . | | | //! . | 1 v 6 | //! . inwelling() <---- build.rs ----> bindings.rs //! .[inwelling crate] [common ancestor] //! ``` //! //! The information in section `[package.metadata.inwelling.{common ancestor}.*]` //! in downstream crates' Cargo.toml files will be collected by `inwelling()`. //! //! # Examples //! //! See this [demo](https://github.com/oooutlk/inwelling/tree/main/examples/) //! for more. //! //! The `echo` crate has build-dependency of inwelling crate: //! //! ```toml //! [build-dependencies] //! inwelling = { path = "../.." } //! ``` //! //! And provides `echo()` which simply returns what it recieves as strings. //! //! In `build.rs`: //! //! ```rust,no_run //! use std::{env, fs, path::PathBuf}; //! //! fn main() { //! let metadata_from_downstream = inwelling::inwelling() //! .sections //! .into_iter() //! .fold( String::new(), |acc, section| //! format!( "{}{:?} <{}>: {}\n" //! , acc //! , section.manifest //! , section.pkg //! , section.metadata.to_string() )); //! //! let out_path = PathBuf::from( env::var( "OUT_DIR" ) //! .expect( "$OUT_DIR should exist." ) //! ).join( "metadata_from_downstream" ); //! //! fs::write( //! out_path, //! metadata_from_downstream //! ).expect( "metadata_from_downstream generated." ); //! } //! ``` //! //! In `lib.rs`: //! //! ```rust,no_run //! pub fn echo() -> String { //! include_str!( concat!( env!( "OUT_DIR" ), "/metadata_from_downstream" )) //! .to_owned() //! } //! ``` //! //! The gamma crate depends on alpha crate and conditionally depends on beta crate. //! The beta crate depends on alpha crate. The alpha, beta and gamma ccrates all //! depend on echo crate. //! //! ```text //! . +---------------> [gamma crate] gamma=true //! . | . ^ ^ //! . | gamma=true . | | //! . | . | | //! . | [beta crate] | beta=true //! . | | | | //! . | beta=true | | | //! . | | | | //! . | [alpha crate] alpha=true //! . | | | | //! . | alpha=true | | | //! . | v | | //! . inwelling() <---- build.rs ----> `echo()`----+ //! .[inwelling crate] [echo crate] //! ``` //! //! In alpha crate's test code: //! //! ```rust,no_run //! pub fn test() { //! let metadata = echo::echo(); //! assert!( metadata.find("<alpha>: {\"alpha\":true}\n").is_some() ); //! } //! ``` //! //! # Optional Metadata //! //! Cargo features can control whether to send metadata or not. in section //! `[package.metadata.inwelling-{common ancestor}]`, a value of `feature = blah` //! means that the metadata will be collected by inwelling if and only if blah //! feature is enabled. See beta crate in examples for more. //! //! # Caveat //! //! ## Reverse Dependency //! //! Collecting metadata from downstream and utilizing it in build process makes a //! crate depending on its downstream crates. Unfortunately this kind of //! reverse-dependency is not known to cargo. As a result, the changing of metadata //! caused by modification of Cargo.toml files or changing of feature set will not //! cause recompilation of the crate collecting metadata, which it should. //! //! To address this issue, simply do `cargo clean`, or more precisely, //! `cargo clean --package {crate-collecting-metadata}` before running //! `cargo build`. Substitute `{crate-collecting-metadata}` with actual crate name, //! e.g. `cargo clean --package echo` in the examples above. //! //! ## Lacking Of `PWD` Environment Variable On Windows //! //! Without official support from cargo, this library requires environment variable //! such as `PWD` to locate topmost crate's Cargo.toml. Unfortunately `PWD` is //! missing on Windows platform. This library will panic if it is feeling no luck to //! locate Cargo.toml. However, `PWD` is not mandatory, unless `inwelling()` told //! you so. use cargo_metadata::{ CargoOpt, MetadataCommand, }; use pals::Pid; use std::{ collections::HashMap, env, path::{Path, PathBuf}, process, }; /// Metadata collected from downstream crates. #[derive( Debug )] pub struct Inwelling { /// sections gathered from downstream Cargo.toml files pub sections : Vec<Section>, } impl Default for Inwelling { fn default() -> Self { Inwelling{ sections: Vec::new() } } } /// Metadata collected from downstream crates, in `[package.metadata.inwelling.*]` sections. #[derive( Debug )] pub struct Section { /// name of the package which collects metadata from its downstream crates. pub pkg : String, /// path of Cargo.toml. pub manifest : PathBuf, /// metadata represented in JSON. pub metadata : serde_json::value::Value, } /// Collects metadata from `[package.metadata.inwelling.*]` sections in downstream crates' Cargo.toml files. pub fn inwelling() -> Inwelling { let mut command = MetadataCommand::new(); let mut manifest_path = None; let mut target_dir_defined_in_cmdline = false; let pals = pals::pals(); if let Ok( pals ) = pals { if let Some( parent ) = pals.parent_of( Pid( process::id() )) { if let Some( parent ) = pals.parent_of( parent.ppid ) { let mut argv = parent.argv(); while let Some( arg ) = argv.next() { match arg { "--all-features" => { command.features( CargoOpt::AllFeatures ); }, "--features" => if let Some( features ) = argv.next() { command.features( CargoOpt::SomeFeatures( features .split_ascii_whitespace() .map( ToOwned::to_owned ) .collect() )); }, "--no-default-features" => { command.features( CargoOpt::NoDefaultFeatures ); }, "--manifest-path" if cfg!( unix ) => if let Some( path ) = argv.next() { manifest_path = Some( PathBuf::from( path )); } "--target-dir" => target_dir_defined_in_cmdline = true, _ => (), } } } } } let manifest_path = manifest_path.unwrap_or_else( || if let Ok( cwd ) = env::var("PWD") { return PathBuf::from( cwd ).join( "Cargo.toml" ); } else { if !target_dir_defined_in_cmdline { if let Ok( out_dir ) = env::var("OUT_DIR") { let out_dir = Path::new( &out_dir ); let ancestors = out_dir.ancestors(); if let Some( manifest_dir ) = ancestors.skip(5).next() { return manifest_dir.join( "Cargo.toml" ); } } } panic!("Failed to locate manifest path. Consider providing PWD environment variable.") } ); if !manifest_path.exists() { panic!( "{:?} should be manifest file", manifest_path ); } let metadata = command .manifest_path( &manifest_path ) .exec() .expect("cargo metadata command should be executed successfully."); let build_name = env::var("CARGO_PKG_NAME").expect("CARGO_PKG_NAME"); let enabled_features = metadata.resolve.expect("package dependencies resolved.").nodes.iter().fold( HashMap::new(), |mut map, node| { map.insert( node.id.clone(), node.features.clone() ); map }); metadata.packages.into_iter().fold( Inwelling::default(), |mut inwelling, mut pkg| { let pkg_id = pkg.id.clone(); let enabled = pkg.metadata .get( &format!( "inwelling-{}", &build_name )) .and_then( |section| section.get( "feature" )) .and_then( |feature| { let feature = feature.as_str().expect("feature name should be str."); Some( enabled_features[ &pkg_id ].iter().find( |&enabled_feature| enabled_feature == &feature ).is_some() ) }) .unwrap_or( true ); if enabled { if let Some( section ) = pkg.metadata.get_mut("inwelling") { if let Some( metadata ) = section.get_mut( &build_name ) { inwelling.sections.push( Section{ pkg : pkg.name, manifest : pkg.manifest_path, metadata : metadata.take(), }); } } } inwelling }) }