Use the crate name instead of the package name

This doesn't work because it uses the name of the build script, which is
always build_script_build. I'm not sure what to change it to - the name
of the library crate could be different than the name of the package,
and there could be multiple different crates being compiled in the same
package.

src/cargo/core/compiler/custom_build.rs

@@ -4,7 +4,6 @@ use crate::core::compiler::context::Metadata;
 use crate::core::compiler::job_queue::JobState;
 use crate::core::{profiles::ProfileRoot, PackageId};
 use crate::util::errors::{CargoResult, CargoResultExt};
-use crate::util::interning::InternedString;
 use crate::util::machine_message::{self, Message};
 use crate::util::{self, internal, paths, profile};
 use cargo_platform::Cfg;
@@ -268,7 +267,7 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
             }
         })
         .collect::<Vec<_>>();
-    let pkg_name = unit.pkg.name();
+    let crate_name = unit.target.crate_name();
     let pkg_descr = unit.pkg.to_string();
     let build_script_outputs = Arc::clone(&cx.build_script_outputs);
     let id = unit.pkg.package_id();
@@ -278,7 +277,7 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
     let host_target_root = cx.files().host_dest().to_path_buf();
     let all = (
         id,
-        pkg_name,
+        crate_name.clone(),
         pkg_descr.clone(),
         Arc::clone(&build_script_outputs),
         output_file.clone(),
@@ -398,7 +397,7 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
         paths::write(&root_output_file, util::path2bytes(&script_out_dir)?)?;
         let parsed_output = BuildOutput::parse(
             &output.stdout,
-            pkg_name,
+            crate_name,
             &pkg_descr,
             &script_out_dir,
             &script_out_dir,
@@ -420,12 +419,12 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
     // itself to run when we actually end up just discarding what we calculated
     // above.
     let fresh = Work::new(move |state| {
-        let (id, pkg_name, pkg_descr, build_script_outputs, output_file, script_out_dir) = all;
+        let (id, crate_name, pkg_descr, build_script_outputs, output_file, script_out_dir) = all;
         let output = match prev_output {
             Some(output) => output,
             None => BuildOutput::parse_file(
                 &output_file,
-                pkg_name,
+                crate_name,
                 &pkg_descr,
                 &prev_script_out_dir,
                 &script_out_dir,
@@ -477,7 +476,7 @@ fn insert_warnings_in_build_outputs(
 impl BuildOutput {
     pub fn parse_file(
         path: &Path,
-        pkg_name: InternedString,
+        crate_name: String,
         pkg_descr: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
@@ -487,7 +486,7 @@ impl BuildOutput {
         let contents = paths::read_bytes(path)?;
         BuildOutput::parse(
             &contents,
-            pkg_name,
+            crate_name,
             pkg_descr,
             script_out_dir_when_generated,
             script_out_dir,
@@ -497,10 +496,12 @@ impl BuildOutput {
     }
 
     // Parses the output of a script.
-    // The `pkg_name` is used for error messages.
+    // The `pkg_descr` is used for error messages.
+    // The `crate_name` is used for determining if RUSTC_BOOTSTRAP should be allowed.
     pub fn parse(
         input: &[u8],
-        pkg_name: InternedString,
+        // Takes String instead of InternedString so passing `unit.pkg.name()` will give a compile error.
+        crate_name: String,
         pkg_descr: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
@@ -589,13 +590,12 @@ impl BuildOutput {
                         // behavior, so still only give a warning.
                         // NOTE: cargo only allows nightly features on RUSTC_BOOTSTRAP=1, but we
                         // want setting any value of RUSTC_BOOTSTRAP to downgrade this to a warning
-                        // (so that `RUSTC_BOOTSTRAP=pkg_name` will work)
+                        // (so that `RUSTC_BOOTSTRAP=crate_name` will work)
                         let rustc_bootstrap_allows = |name: &str| {
-                            std::env::var("RUSTC_BOOTSTRAP").map_or(false, |var| {
-                                var.split(',').any(|s| s == name)
-                            })
+                            std::env::var("RUSTC_BOOTSTRAP")
+                                .map_or(false, |var| var.split(',').any(|s| s == name))
                         };
-                        if nightly_features_allowed || rustc_bootstrap_allows(&*pkg_name) {
+                        if nightly_features_allowed || rustc_bootstrap_allows(&*crate_name) {
                             warnings.push(format!("Cannot set `RUSTC_BOOTSTRAP={}` from {}.\n\
                                 note: Crates cannot set `RUSTC_BOOTSTRAP` themselves, as doing so would subvert the stability guarantees of Rust for your project.",
                                 val, whence
@@ -608,7 +608,7 @@ impl BuildOutput {
                                 help: If you're sure you want to do this in your project, set the environment variable `RUSTC_BOOTSTRAP={}` before running cargo instead.",
                                 val,
                                 whence,
-                                pkg_name,
+                                crate_name,
                             );
                         }
                     } else {
@@ -865,7 +865,7 @@ fn prev_build_output(cx: &mut Context<'_, '_>, unit: &Unit) -> (Option<BuildOutp
     (
         BuildOutput::parse_file(
             &output_file,
-            unit.pkg.name(),
+            unit.target.crate_name(),
             &unit.pkg.to_string(),
             &prev_script_out_dir,
             &script_out_dir,

tests/testsuite/build_script_env.rs

@@ -1,5 +1,6 @@
 //! Tests for build.rs rerun-if-env-changed and rustc-env
 
+use cargo_test_support::basic_manifest;
 use cargo_test_support::project;
 use cargo_test_support::sleep_ms;
 
@@ -110,6 +111,7 @@ fn rerun_if_env_or_file_changes() {
 #[cargo_test]
 fn rustc_bootstrap() {
     let p = project()
+        .file("Cargo.toml", &basic_manifest("has-dashes", "0.0.1"))
         .file("src/main.rs", "fn main() {}")
         .file(
             "build.rs",
@@ -122,7 +124,9 @@ fn rustc_bootstrap() {
         .build();
     p.cargo("build")
         .with_stderr_contains("error: Cannot set `RUSTC_BOOTSTRAP=1` [..]")
-        .with_stderr_contains("help: [..] set the environment variable `RUSTC_BOOTSTRAP=foo` [..]")
+        .with_stderr_contains(
+            "help: [..] set the environment variable `RUSTC_BOOTSTRAP=has_dashes` [..]",
+        )
         .with_status(101)
         .run();
     p.cargo("build")
@@ -131,14 +135,16 @@ fn rustc_bootstrap() {
         .run();
     // RUSTC_BOOTSTRAP set to the name of the crate
     p.cargo("build")
-        .env("RUSTC_BOOTSTRAP", "foo")
+        .env("RUSTC_BOOTSTRAP", "has_dashes")
         .with_stderr_contains("warning: Cannot set `RUSTC_BOOTSTRAP=1` [..]")
         .run();
     // RUSTC_BOOTSTRAP set to some random value
     p.cargo("build")
         .env("RUSTC_BOOTSTRAP", "bar")
         .with_stderr_contains("error: Cannot set `RUSTC_BOOTSTRAP=1` [..]")
-        .with_stderr_contains("help: [..] set the environment variable `RUSTC_BOOTSTRAP=foo` [..]")
+        .with_stderr_contains(
+            "help: [..] set the environment variable `RUSTC_BOOTSTRAP=has_dashes` [..]",
+        )
         .with_status(101)
         .run();
 }