From f4e75dc0459d4c4bc2603ea456afd26bcde9c074 Mon Sep 17 00:00:00 2001
From: Christoph Gehrke <christoph@srlabs.de>
Date: Wed, 1 Apr 2026 15:44:58 +0200
Subject: [PATCH] fix(cover): check for grcov's dependencies

Doing this before profiling the corpus can save some frustration when
llvm-tools are missing.
---
 Cargo.toml                      |  5 ++---
 src/bin/cargo-ziggy/coverage.rs | 18 +++++++++++++++++-
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index c0f36ad..aed564c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -28,6 +28,7 @@ cli = [
     "signal-hook",
     "strip-ansi-escapes",
     "target-triple",
+    "tempfile",
     "time-humanize",
     "twox-hash",
 ]
@@ -48,11 +49,9 @@ semver = { version = "1.0.27", optional = true }
 signal-hook = { version = "0.4.3", optional = true }
 strip-ansi-escapes = { version = "0.2.1", optional = true }
 target-triple = { version = "1.0.0", optional = true }
+tempfile = { version = "3.27.0", optional = true }
 time-humanize = { version = "0.1.3", optional = true }
 twox-hash = { version = "2.1.2", optional = true }
 
-[dev-dependencies]
-tempfile = "3"
-
 [lints.clippy]
 needless_doctest_main = "allow"
diff --git a/src/bin/cargo-ziggy/coverage.rs b/src/bin/cargo-ziggy/coverage.rs
index c00f8c0..e88f1d1 100644
--- a/src/bin/cargo-ziggy/coverage.rs
+++ b/src/bin/cargo-ziggy/coverage.rs
@@ -1,5 +1,5 @@
 use crate::{Cover, find_target};
-use anyhow::{Context, Result, bail};
+use anyhow::{Context, Result, anyhow, bail};
 use cargo_metadata::camino::Utf8PathBuf;
 use glob::glob;
 use indicatif::{ProgressBar, ProgressStyle};
@@ -22,6 +22,22 @@ impl Cover {
             .output()
             .context("grcov not found - please install by running `cargo install grcov`")?;
 
+        if let Ok(dir) = tempfile::tempdir() {
+            const TAG: &str = "[ERROR] ";
+            let _ = std::fs::File::create(dir.path().join("a.profraw"));
+            if let Some(out) = process::Command::new("grcov")
+                .args(["-b=.", "-o=.", "."])
+                .current_dir(dir.path())
+                .output()
+                .ok()
+                .and_then(|o| String::from_utf8(o.stderr).ok())
+                && let Some(idx) = out.find(TAG)
+            {
+                return Err(anyhow!("{}", &out[idx + TAG.len()..]))
+                    .context("grcov missing dependencies");
+            }
+        }
+
         eprintln!("Generating coverage");
 
         self.target =