-Zrustdoc-scrape-example must fail with bad build script

src/cargo/core/compiler/rustdoc.rs

@@ -211,16 +211,24 @@ impl RustdocScrapeExamples {
 }
 
 impl BuildContext<'_, '_> {
-    /// Returns the set of Docscrape units that have a direct dependency on `unit`
+    /// Returns the set of [`Docscrape`] units that have a direct dependency on `unit`.
+    ///
+    /// [`RunCustomBuild`] units are excluded because we allow failures
+    /// from type checks but not build script executions.
+    /// A plain old `cargo doc` would just die if a build script execution fails,
+    /// there is no reason for `-Zrustdoc-scrape-examples` to keep going.
+    ///
+    /// [`Docscrape`]: crate::core::compiler::CompileMode::Docscrape
+    /// [`RunCustomBuild`]: crate::core::compiler::CompileMode::Docscrape
     pub fn scrape_units_have_dep_on<'a>(&'a self, unit: &'a Unit) -> Vec<&'a Unit> {
         self.scrape_units
             .iter()
             .filter(|scrape_unit| {
                 self.unit_graph[scrape_unit]
                     .iter()
-                    .any(|dep| &dep.unit == unit)
+                    .any(|dep| &dep.unit == unit && !dep.unit.mode.is_run_custom_build())
             })
-            .collect::<Vec<_>>()
+            .collect()
     }
 
     /// Returns true if this unit is needed for doing doc-scraping and is also

tests/testsuite/docscrape.rs

@@ -366,6 +366,37 @@ warning: `foo` (example \"ex2\") generated 1 warning
         .run();
 }
 
+#[cargo_test(nightly, reason = "rustdoc scrape examples flags are unstable")]
+fn fail_bad_build_script() {
+    // See rust-lang/cargo#11623
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.0.1"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file("build.rs", "fn main() { panic!(\"You shall not pass\")}")
+        .file("examples/ex.rs", "fn main() {}")
+        .build();
+
+    // `cargo doc` fails
+    p.cargo("doc")
+        .with_status(101)
+        .with_stderr_contains("[..]You shall not pass[..]")
+        .run();
+
+    // scrape examples should fail whenever `cargo doc` fails.
+    p.cargo("doc -Zunstable-options -Z rustdoc-scrape-examples")
+        .masquerade_as_nightly_cargo(&["rustdoc-scrape-examples"])
+        .with_status(101)
+        .with_stderr_contains("[..]You shall not pass[..]")
+        .run();
+}
+
 #[cargo_test(nightly, reason = "rustdoc scrape examples flags are unstable")]
 fn no_fail_bad_example() {
     let p = project()