Skip crates without lib targets; exit non-zero if nothing to check. (#477)

* Skip crates without lib targets; exit non-zero if nothing to check.

* Delint.

Author: obi1kenobi

src/lib.rs

@@ -216,7 +216,11 @@ impl Scope {
 
         meta.packages
             .iter()
-            .filter(|&p| base_ids.contains(&p.id))
+            .filter(|&p| {
+                // The package has to not have been explicitly excluded,
+                // and also has to have a library target (an API we can check).
+                base_ids.contains(&p.id) && p.targets.iter().any(|target| target.is_lib())
+            })
             .collect()
     }
 }
@@ -437,6 +441,12 @@ impl Check {
             RustdocSource::Root(project_root) => {
                 let metadata = manifest_metadata(project_root)?;
                 let selected = self.scope.selected_packages(&metadata);
+                if selected.is_empty() {
+                    anyhow::bail!(
+                        "no crates with library targets selected, nothing to semver-check"
+                    );
+                }
+
                 selected
                     .iter()
                     .map(|selected| {

test_crates/crate_in_workspace/Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-members = ["crate1"]
+members = ["lib_crate", "non_lib_crate"]
 
 [workspace.package]
 version = "0.1.0"

test_crates/crate_in_workspace/crate1/Cargo.toml test_crates/crate_in_workspace/lib_crate/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 publish = false
-name = "crate_in_workspace_crate1"
+name = "lib_crate"
 version = { workspace = true }
 
 [dependencies]

test_crates/crate_in_workspace/crate1/src/lib.rs test_crates/crate_in_workspace/lib_crate/src/lib.rs

@@ -0,0 +1,8 @@
+[package]
+name = "non_lib_crate"
+edition = "2021"
+version.workspace = true
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

test_crates/crate_in_workspace/non_lib_crate/Cargo.toml

@@ -0,0 +1 @@
+fn main() {}

test_crates/crate_in_workspace/non_lib_crate/src/main.rs

@@ -24,14 +24,16 @@ fn lib_target_with_dashes() {
         .success();
 }
 
-/// Ensure that proc macro crates can be semver-checked correctly.
+/// Ensure that proc macro crates without a lib target produce the correct error message
+/// since they have no library API and therefore nothing we can semver-check.
 #[test]
 fn proc_macro_target() {
     let mut cmd = Command::cargo_bin("cargo-semver-checks").unwrap();
     cmd.current_dir("test_crates/proc_macro_crate")
         .args(["semver-checks", "check-release", "--baseline-root=."])
         .assert()
-        .success();
+        .stderr("Error: no crates with library targets selected, nothing to semver-check\n")
+        .failure();
 }
 
 /// Ensure that crates whose lib targets have a different name can be semver-checked correctly.
@@ -69,11 +71,27 @@ fn crate_in_workspace() {
             "check-release",
             "--manifest-path=./Cargo.toml",
             "-p",
-            "crate1",
+            "lib_crate",
             "--baseline-root=.",
         ])
         .assert()
         .success();
+
+    // Run at workspace level then point out a crate without a lib target.
+    // This should produce an error and a non-zero exit code.
+    let mut cmd = Command::cargo_bin("cargo-semver-checks").unwrap();
+    cmd.current_dir("test_crates/crate_in_workspace")
+        .args([
+            "semver-checks",
+            "check-release",
+            "--manifest-path=./Cargo.toml",
+            "-p",
+            "non_lib_crate",
+            "--baseline-root=.",
+        ])
+        .assert()
+        .stderr("Error: no crates with library targets selected, nothing to semver-check\n")
+        .failure();
 }
 
 /// This test ensures that the `--release-type` flag works correctly,