prepare: report a structured error when a dependency is missing

Author: pietroalbini

CHANGELOG.md

@@ -5,6 +5,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+- New variant `PrepareError::MissingDependencies`, returned during the prepare
+  step when a dependency does not exist.
+
 ### Changed
 
 - Path dependencies are no longer removed from `Cargo.toml` during the prepare

src/prepare.rs

@@ -96,6 +96,7 @@ impl<'a> Prepare<'a> {
         }
 
         let mut yanked_deps = false;
+        let mut missing_deps = false;
         let mut cmd = Command::new(self.workspace, self.toolchain.cargo()).args(&[
             "generate-lockfile",
             "--manifest-path",
@@ -111,13 +112,20 @@ impl<'a> Prepare<'a> {
             .process_lines(&mut |line, _| {
                 if line.contains("failed to select a version for the requirement") {
                     yanked_deps = true;
+                } else if line.contains("failed to load source for dependency")
+                    || line.contains("no matching package named")
+                {
+                    missing_deps = true;
                 }
             })
             .run();
         match res {
             Err(_) if yanked_deps => {
                 return Err(PrepareError::YankedDependencies.into());
             }
+            Err(_) if missing_deps => {
+                return Err(PrepareError::MissingDependencies.into());
+            }
             other => other?,
         }
         self.lockfile_captured = true;
@@ -349,6 +357,9 @@ pub enum PrepareError {
     /// Some of this crate's dependencies were yanked, preventing Crater from fetching them.
     #[fail(display = "the crate depends on yanked dependencies")]
     YankedDependencies,
+    /// Some of the dependencies do not exist anymore.
+    #[fail(display = "the crate depends on missing dependencies")]
+    MissingDependencies,
 }
 
 #[cfg(test)]

tests/buildtest/crates/missing-deps-git/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "missing-deps"
+version = "0.1.0"
+authors = ["Pietro Albini <pietro@pietroalbini.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+not-a-git-repo = { git = "https://www.example.com/definitely-not-a-git-repo.git" }

tests/buildtest/crates/missing-deps-git/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

tests/buildtest/crates/missing-deps-registry/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "missing-deps-registry"
+version = "0.1.0"
+authors = ["Pietro Albini <pietro@pietroalbini.org>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+# The `macro` crate name is reserved on crates.io.
+macro = "*"

tests/buildtest/crates/missing-deps-registry/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

tests/buildtest/mod.rs

@@ -131,3 +131,15 @@ test_prepare_error!(
 );
 
 test_prepare_error!(test_yanked_deps, "yanked-deps", YankedDependencies);
+
+test_prepare_error!(
+    test_missing_deps_git,
+    "missing-deps-git",
+    MissingDependencies
+);
+
+test_prepare_error!(
+    test_missing_deps_registry,
+    "missing-deps-registry",
+    MissingDependencies
+);