ci: Add lint to check if all sub-crates features can be enabled from ruma crate

xtask/src/cargo.rs

@@ -1,9 +1,14 @@
-use std::path::PathBuf;
+#![allow(clippy::disallowed_types)]
 
+use std::{collections::HashMap, path::PathBuf};
+
+#[cfg(feature = "default")]
 use reqwest::blocking::Client;
 use semver::Version;
 use serde::{de::IgnoredAny, Deserialize};
+#[cfg(feature = "default")]
 use toml_edit::{value, Document};
+#[cfg(feature = "default")]
 use xshell::{cmd, pushd, read_file, write_file};
 
 use crate::{util::ask_yes_no, Metadata, Result};
@@ -22,11 +27,51 @@ pub struct Package {
     /// The package's manifest path.
     pub manifest_path: PathBuf,
 
-    /// A map of the package dependencies.
+    /// A list of the package dependencies.
     #[serde(default)]
     pub dependencies: Vec<Dependency>,
+
+    /// A map of the package features.
+    #[serde(default)]
+    pub features: HashMap<String, Vec<String>>,
 }
 
+impl Package {
+    /// Whether this package has a way to enable the given feature from the given package.
+    pub fn can_enable_feature(&self, package_name: &str, feature_name: &str) -> bool {
+        for activated_feature in self.features.values().flatten() {
+            // Remove optional `dep:` at the start.
+            let remaining = activated_feature.trim_start_matches("dep:");
+
+            // Check that we have the package name.
+            let Some(remaining) = remaining.strip_prefix(package_name) else {
+                continue;
+            };
+
+            if remaining.is_empty() {
+                // The feature only enables the dependency.
+                continue;
+            }
+
+            // Remove optional `?`.
+            let remaining = remaining.trim_start_matches('?');
+
+            let Some(remaining) = remaining.strip_prefix('/') else {
+                // This is another package name starting with the same string.
+                continue;
+            };
+
+            // Finally, only the feature name is remaining.
+            if remaining == feature_name {
+                return true;
+            }
+        }
+
+        false
+    }
+}
+
+#[cfg(feature = "default")]
 impl Package {
     /// Update the version of this crate.
     pub fn update_version(&mut self, version: &Version, dry_run: bool) -> Result<()> {
@@ -203,6 +248,7 @@ pub enum DependencyKind {
     Build,
 }
 
+#[cfg(feature = "default")]
 /// A crate from the `GET /crates/{crate}` endpoint of crates.io.
 #[derive(Deserialize)]
 struct CratesIoCrate {

xtask/src/ci.rs

@@ -1,15 +1,17 @@
 // Triggers at the `#[clap(subcommand)]` line, but not easily reproducible outside this crate.
 #![allow(unused_qualifications)]
 
-use std::path::PathBuf;
+use std::path::Path;
 
 use clap::{Args, Subcommand};
 use xshell::pushd;
 
 use crate::{cmd, Metadata, Result, NIGHTLY};
 
+mod reexport_features;
 mod spec_links;
 
+use reexport_features::check_reexport_features;
 use spec_links::check_spec_links;
 
 const MSRV: &str = "1.75";
@@ -66,6 +68,8 @@ pub enum CiCmd {
     Dependencies,
     /// Check spec links point to a recent version (lint)
     SpecLinks,
+    /// Check all cargo features of sub-crates can be enabled from ruma (lint)
+    ReexportFeatures,
     /// Check typos
     Typos,
 }
@@ -75,18 +79,22 @@ pub struct CiTask {
     /// Which command to run.
     cmd: Option<CiCmd>,
 
-    /// The root of the workspace.
-    project_root: PathBuf,
+    /// The metadata of the workspace.
+    project_metadata: Metadata,
 }
 
 impl CiTask {
     pub(crate) fn new(cmd: Option<CiCmd>) -> Result<Self> {
-        let project_root = Metadata::load()?.workspace_root;
-        Ok(Self { cmd, project_root })
+        let project_metadata = Metadata::load()?;
+        Ok(Self { cmd, project_metadata })
+    }
+
+    fn project_root(&self) -> &Path {
+        &self.project_metadata.workspace_root
     }
 
     pub(crate) fn run(self) -> Result<()> {
-        let _p = pushd(&self.project_root)?;
+        let _p = pushd(self.project_root())?;
 
         match self.cmd {
             Some(CiCmd::Msrv) => self.msrv()?,
@@ -110,7 +118,8 @@ impl CiTask {
             Some(CiCmd::ClippyAll) => self.clippy_all()?,
             Some(CiCmd::Lint) => self.lint()?,
             Some(CiCmd::Dependencies) => self.dependencies()?,
-            Some(CiCmd::SpecLinks) => check_spec_links(&self.project_root.join("crates"))?,
+            Some(CiCmd::SpecLinks) => check_spec_links(&self.project_root().join("crates"))?,
+            Some(CiCmd::ReexportFeatures) => check_reexport_features(&self.project_metadata)?,
             Some(CiCmd::Typos) => self.typos()?,
             None => {
                 self.msrv()
@@ -301,9 +310,11 @@ impl CiTask {
         // Check dependencies being sorted
         let dependencies_res = self.dependencies();
         // Check that all links point to the same version of the spec
-        let spec_links_res = check_spec_links(&self.project_root.join("crates"));
+        let spec_links_res = check_spec_links(&self.project_root().join("crates"));
+        // Check that all cargo features of sub-crates can be enabled from ruma.
+        let reexport_features_res = check_reexport_features(&self.project_metadata);
 
-        dependencies_res.and(spec_links_res)
+        dependencies_res.and(spec_links_res).and(reexport_features_res)
     }
 
     /// Check the sorting of dependencies with the nightly version.

xtask/src/ci/reexport_features.rs

@@ -0,0 +1,54 @@
+use crate::{Metadata, Result};
+
+/// Check that the ruma crate allows to enable all the features of the other ruma-* crates.
+///
+/// For simplicity, this function assumes that:
+///
+/// - Those dependencies are not renamed.
+/// - ruma does not use `default-features = false` on those dependencies.
+///
+/// This does not check if all features are re-exported individually, as that is not always wanted.
+pub(crate) fn check_reexport_features(metadata: &Metadata) -> Result<()> {
+    println!("Checking all features can be enabled from ruma…");
+    let mut n_errors = 0;
+
+    let Some(ruma) = metadata.find_package("ruma") else {
+        return Err("ruma package not found in workspace".into());
+    };
+
+    for package in ruma.dependencies.iter().filter_map(|dep| metadata.find_package(&dep.name)) {
+        println!("Checking features of {}…", package.name);
+
+        // Exclude ruma and xtask.
+        if !package.name.starts_with("ruma-") {
+            continue;
+        }
+
+        // Filter features that are enabled by other features of the same package.
+        let features = package.features.keys().filter(|feature_name| {
+            !package.features.values().flatten().any(|activated_feature| {
+                activated_feature.trim_start_matches("dep:") == *feature_name
+            })
+        });
+
+        for feature_name in features {
+            // Let's assume that ruma never has `default-features = false`.
+            if feature_name == "default" {
+                continue;
+            }
+
+            if !ruma.can_enable_feature(&package.name, feature_name) {
+                println!(r#"  Missing feature "{}/{feature_name}""#, package.name);
+                n_errors += 1;
+            }
+        }
+    }
+
+    if n_errors > 0 {
+        // Visual aid to separate the end error message.
+        println!();
+        return Err(format!("Found {n_errors} missing features").into());
+    }
+
+    Ok(())
+}

xtask/src/main.rs

@@ -17,7 +17,6 @@ use serde_json::from_str as from_json_str;
 // Keep in sync with version in `rust-toolchain.toml` and `.github/workflows/ci.yml`
 const NIGHTLY: &str = "nightly-2024-02-14";
 
-#[cfg(feature = "default")]
 mod cargo;
 mod ci;
 mod doc;
@@ -26,6 +25,7 @@ mod release;
 #[cfg(feature = "default")]
 mod util;
 
+use cargo::Package;
 use ci::{CiArgs, CiTask};
 use doc::DocTask;
 #[cfg(feature = "default")]
@@ -70,8 +70,7 @@ fn main() -> Result<()> {
 #[derive(Clone, Debug, Deserialize)]
 struct Metadata {
     pub workspace_root: PathBuf,
-    #[cfg(feature = "default")]
-    pub packages: Vec<cargo::Package>,
+    pub packages: Vec<Package>,
 }
 
 impl Metadata {
@@ -80,6 +79,11 @@ impl Metadata {
         let metadata_json = cmd!("cargo metadata --no-deps --format-version 1").read()?;
         Ok(from_json_str(&metadata_json)?)
     }
+
+    /// Find the package with the given name.
+    pub fn find_package(&self, name: &str) -> Option<&Package> {
+        self.packages.iter().find(|p| p.name == name)
+    }
 }
 
 #[cfg(feature = "default")]