xtask: Add action to generate a code coverage report

This uses llvm-cov (https://github.com/taiki-e/cargo-llvm-cov) to create a
simple HTML code coverage report.

For now this only includes coverage from host tests, but in the future we can
use https://github.com/Amanieu/minicov to include coverage from VM tests as
well.

Author: nicholasbishop

xtask/src/cargo.rs

@@ -186,6 +186,9 @@ impl TargetTypes {
 pub enum CargoAction {
     Build,
     Clippy,
+    Coverage {
+        open: bool,
+    },
     Doc {
         open: bool,
         document_private_items: bool,
@@ -251,6 +254,13 @@ impl Cargo {
                     tool_args.extend(["-D", "warnings"]);
                 }
             }
+            CargoAction::Coverage { open } => {
+                action = "llvm-cov";
+                extra_args.push("--html");
+                if open {
+                    extra_args.push("--open");
+                }
+            }
             CargoAction::Doc {
                 open,
                 document_private_items,

xtask/src/main.rs

@@ -12,12 +12,12 @@ mod tpm;
 mod util;
 
 use crate::opt::{FmtOpt, TestOpt};
-use anyhow::Result;
+use anyhow::{bail, Result};
 use arch::UefiArch;
 use cargo::{Cargo, CargoAction, Feature, Package, TargetTypes};
 use clap::Parser;
 use itertools::Itertools;
-use opt::{Action, BuildOpt, ClippyOpt, DocOpt, Opt, QemuOpt, TpmVersion};
+use opt::{Action, BuildOpt, ClippyOpt, CovOpt, DocOpt, Opt, QemuOpt, TpmVersion};
 use std::process::Command;
 use util::run_cmd;
 
@@ -85,6 +85,27 @@ fn clippy(opt: &ClippyOpt) -> Result<()> {
     run_cmd(cargo.command()?)
 }
 
+/// Generate a code coverage report.
+fn code_coverage(opt: &CovOpt) -> Result<()> {
+    if has_cmd("cargo-llvm-cov") {
+        let cargo = Cargo {
+            action: CargoAction::Coverage { open: opt.open },
+            features: Feature::more_code(*opt.unstable, false),
+            // Leave out uefi-macros; the compilation tests will just make
+            // things slower without contributing anything to the coverage
+            // report.
+            packages: vec![Package::UefiRaw, Package::Uefi],
+            release: false,
+            target: None,
+            warnings_as_errors: false,
+            target_types: TargetTypes::Default,
+        };
+        run_cmd(cargo.command()?)
+    } else {
+        bail!("cargo-llvm-cov not found, see https://github.com/taiki-e/cargo-llvm-cov");
+    }
+}
+
 /// Build docs.
 fn doc(opt: &DocOpt) -> Result<()> {
     let cargo = Cargo {
@@ -305,6 +326,7 @@ fn main() -> Result<()> {
         Action::Build(build_opt) => build(build_opt),
         Action::CheckRaw(_) => check_raw::check_raw(),
         Action::Clippy(clippy_opt) => clippy(clippy_opt),
+        Action::Cov(cov_opt) => code_coverage(cov_opt),
         Action::Doc(doc_opt) => doc(doc_opt),
         Action::GenCode(gen_opt) => device_path::gen_code(gen_opt),
         Action::Miri(_) => run_miri(),

xtask/src/opt.rs

@@ -68,6 +68,7 @@ pub enum Action {
     Build(BuildOpt),
     CheckRaw(CheckRawOpt),
     Clippy(ClippyOpt),
+    Cov(CovOpt),
     Doc(DocOpt),
     GenCode(GenCodeOpt),
     Miri(MiriOpt),
@@ -105,6 +106,17 @@ pub struct ClippyOpt {
     pub warning: WarningOpt,
 }
 
+/// Generate a code coverage report.
+#[derive(Debug, Parser)]
+pub struct CovOpt {
+    /// Open the output in a browser.
+    #[clap(long, action)]
+    pub open: bool,
+
+    #[clap(flatten)]
+    pub unstable: UnstableOpt,
+}
+
 /// Build the docs for the uefi packages.
 #[derive(Debug, Parser)]
 pub struct DocOpt {