Reinstate ci_rustc_if_unchanged tests

This time without the dummy commit.

Author: Kobzol

src/bootstrap/src/core/builder/tests.rs

@@ -1,11 +1,14 @@
+use std::env::VarError;
 use std::{panic, thread};
 
+use build_helper::stage0_parser::parse_stage0_file;
 use llvm::prebuilt_llvm_config;
 
 use super::*;
 use crate::Flags;
 use crate::core::build_steps::doc::DocumentationFormat;
 use crate::core::config::Config;
+use crate::utils::tests::git::{GitCtx, git_test};
 
 static TEST_TRIPLE_1: &str = "i686-unknown-haiku";
 static TEST_TRIPLE_2: &str = "i686-unknown-hurd-gnu";
@@ -238,6 +241,125 @@ fn alias_and_path_for_library() {
     );
 }
 
+#[test]
+fn ci_rustc_if_unchanged_invalidate_on_compiler_changes() {
+    git_test(|ctx| {
+        prepare_rustc_checkout(ctx);
+        ctx.create_upstream_merge(&["compiler/bar"]);
+        // This change should invalidate download-ci-rustc
+        ctx.create_nonupstream_merge(&["compiler/foo"]);
+
+        let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged");
+        assert_eq!(config.download_rustc_commit, None);
+    });
+}
+
+#[test]
+fn ci_rustc_if_unchanged_invalidate_on_library_changes_in_ci() {
+    git_test(|ctx| {
+        prepare_rustc_checkout(ctx);
+        ctx.create_upstream_merge(&["compiler/bar"]);
+        // This change should invalidate download-ci-rustc
+        ctx.create_nonupstream_merge(&["library/foo"]);
+
+        with_mocked_ci(|| {
+            let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged");
+            assert_eq!(config.download_rustc_commit, None);
+        });
+    });
+}
+
+#[test]
+fn ci_rustc_if_unchanged_do_not_invalidate_on_library_changes_outside_ci() {
+    git_test(|ctx| {
+        prepare_rustc_checkout(ctx);
+        let sha = ctx.create_upstream_merge(&["compiler/bar"]);
+        // This change should not invalidate download-ci-rustc
+        ctx.create_nonupstream_merge(&["library/foo"]);
+
+        with_mocked_outside_ci(|| {
+            let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged");
+            assert_eq!(config.download_rustc_commit, Some(sha));
+        });
+    });
+}
+
+#[test]
+fn ci_rustc_if_unchanged_do_not_invalidate_on_tool_changes() {
+    git_test(|ctx| {
+        prepare_rustc_checkout(ctx);
+        let sha = ctx.create_upstream_merge(&["compiler/bar"]);
+        // This change should not invalidate download-ci-rustc
+        ctx.create_nonupstream_merge(&["src/tools/foo"]);
+
+        let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged");
+        assert_eq!(config.download_rustc_commit, Some(sha));
+    });
+}
+
+/// Temporarily mocks the current environment to make it look like we're in CI.
+/// If we are actually in CI, nothing changes.
+fn with_mocked_ci<F, R>(func: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    if let Err(VarError::NotPresent) = std::env::var("GITHUB_ACTIONS") {
+        // SAFETY: bootstrap tests are sequential
+        unsafe { std::env::set_var("GITHUB_ACTIONS", "true") };
+
+        let ret = func();
+
+        // SAFETY: bootstrap tests are sequential
+        unsafe { std::env::remove_var("GITHUB_ACTIONS") };
+        ret
+    } else {
+        func()
+    }
+}
+
+/// Temporarily mocks the current environment to make it look like we're **NOT** in CI.
+/// If we are actually not in CI, nothing changes.
+fn with_mocked_outside_ci<F, R>(func: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    if let Ok(var) = std::env::var("GITHUB_ACTIONS") {
+        // SAFETY: bootstrap tests are sequential
+        unsafe { std::env::remove_var("GITHUB_ACTIONS") };
+
+        let ret = func();
+
+        // SAFETY: bootstrap tests are sequential
+        unsafe { std::env::set_var("GITHUB_ACTIONS", var) };
+        ret
+    } else {
+        func()
+    }
+}
+
+/// Prepares the given directory so that it looks like a rustc checkout.
+/// Also configures `GitCtx` to use the correct merge bot e-mail for upstream merge commits.
+fn prepare_rustc_checkout(ctx: &mut GitCtx) {
+    ctx.merge_bot_email =
+        format!("Merge bot <{}>", parse_stage0_file().config.git_merge_commit_email);
+    ctx.write("src/ci/channel", "nightly");
+    ctx.commit();
+}
+
+/// Parses a Config directory from `path`, with the given value of `download_rustc`.
+fn parse_config_download_rustc_at(path: &Path, download_rustc: &str) -> Config {
+    Config::parse_inner(
+        Flags::parse(&[
+            "build".to_owned(),
+            "--dry-run".to_owned(),
+            format!("--set=rust.download-rustc='{download_rustc}'"),
+            "--src".to_owned(),
+            path.to_str().unwrap().to_owned(),
+        ]),
+        |&_| Ok(Default::default()),
+    )
+}
+
 mod defaults {
     use pretty_assertions::assert_eq;
 

src/bootstrap/src/core/config/config.rs

@@ -3007,6 +3007,7 @@ impl Config {
         llvm_assertions: bool,
     ) -> Option<String> {
         if !is_download_ci_available(&self.build.triple, llvm_assertions) {
+            eprintln!("DOWNLOAD NOT AVAILABLE");
             return None;
         }
 
@@ -3045,17 +3046,21 @@ impl Config {
             allowed_paths.push(":!library");
         }
 
+        eprintln!("{:?}", self.rust_info);
+        eprintln!("{:?}", self.src);
+        eprintln!("{:?}", self.git_config());
         let commit = if self.rust_info.is_managed_git_subrepository() {
             // Look for a version to compare to based on the current commit.
             // Only commits merged by bors will have CI artifacts.
             let freshness = self.check_path_modifications(&allowed_paths);
-            self.verbose(|| {
-                eprintln!("rustc freshness: {freshness:?}");
-            });
+            // self.verbose(|| {
+            eprintln!("rustc freshness: {freshness:?}");
+            // });
             match freshness {
                 PathFreshness::LastModifiedUpstream { upstream } => upstream,
                 PathFreshness::HasLocalModifications { upstream } => {
                     if if_unchanged {
+                        eprintln!("LOCAL MODIFICATIONS IF UNCHANGED");
                         return None;
                     }
 
@@ -3064,6 +3069,7 @@ impl Config {
                         eprintln!(
                             "`rustc.download-ci` functionality will be skipped as artifacts are not available."
                         );
+                        eprintln!("WE ARE ON CI");
                         return None;
                     }
 
@@ -3085,6 +3091,7 @@ impl Config {
                 "WARN: `rust.debug-assertions = true` will prevent downloading CI rustc as alt CI \
                 rustc is not currently built with debug assertions."
             );
+            eprintln!("REQUESTING DEBUG ASSERTIONS");
             return None;
         }
 

src/bootstrap/src/utils/channel.rs

@@ -12,7 +12,7 @@ use super::helpers;
 use crate::Build;
 use crate::utils::helpers::{start_process, t};
 
-#[derive(Clone, Default)]
+#[derive(Clone, Default, Debug)]
 pub enum GitInfo {
     /// This is not a git repository.
     #[default]
@@ -26,7 +26,7 @@ pub enum GitInfo {
     RecordedForTarball(Info),
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Info {
     pub commit_date: String,
     pub sha: String,

src/bootstrap/src/utils/tests/git.rs

@@ -81,13 +81,17 @@ impl GitCtx {
     }
 
     pub fn modify(&self, path: &str) {
+        self.write(path, "line");
+    }
+
+    pub fn write(&self, path: &str, data: &str) {
         use std::io::Write;
 
         let path = self.dir.path().join(path);
         std::fs::create_dir_all(&path.parent().unwrap()).unwrap();
 
         let mut file = OpenOptions::new().create(true).append(true).open(path).unwrap();
-        writeln!(file, "line").unwrap();
+        writeln!(file, "{data}").unwrap();
     }
 
     pub fn commit(&self) -> String {