From 6ca2a0dd26f2bea3cb681cc98fbc92f34e85209b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jakub=20Ber=C3=A1nek?= <berykubik@gmail.com>
Date: Tue, 8 Apr 2025 14:49:11 +0200
Subject: [PATCH] Extend `ci_rustc_if_unchanged` tests

---
 src/bootstrap/src/core/builder/tests.rs | 103 +++++++++++++++++-------
 src/bootstrap/src/utils/tests/git.rs    |   6 +-
 2 files changed, 77 insertions(+), 32 deletions(-)

diff --git a/src/bootstrap/src/core/builder/tests.rs b/src/bootstrap/src/core/builder/tests.rs
index a2814c7dbf82..8e2c6fc52cd0 100644
--- a/src/bootstrap/src/core/builder/tests.rs
+++ b/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";
@@ -239,42 +242,80 @@ fn alias_and_path_for_library() {
 }
 
 #[test]
-fn ci_rustc_if_unchanged_logic() {
-    let config = Config::parse_inner(
+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", true);
+        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"]);
+
+        let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged", true);
+        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"]);
+
+        let config = parse_config_download_rustc_at(ctx.get_path(), "if-unchanged", false);
+        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", true);
+        assert_eq!(config.download_rustc_commit, Some(sha));
+    });
+}
+
+/// 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, ci: bool) -> Config {
+    Config::parse_inner(
         Flags::parse(&[
             "build".to_owned(),
             "--dry-run".to_owned(),
-            "--set=rust.download-rustc='if-unchanged'".to_owned(),
+            "--ci".to_owned(),
+            if ci { "true" } else { "false" }.to_owned(),
+            format!("--set=rust.download-rustc='{download_rustc}'"),
+            "--src".to_owned(),
+            path.to_str().unwrap().to_owned(),
         ]),
         |&_| Ok(Default::default()),
-    );
-
-    let build = Build::new(config.clone());
-    let builder = Builder::new(&build);
-
-    if config.out.exists() {
-        fs::remove_dir_all(&config.out).unwrap();
-    }
-
-    builder.run_step_descriptions(&Builder::get_step_descriptions(config.cmd.kind()), &[]);
-
-    // Make sure "if-unchanged" logic doesn't try to use CI rustc while there are changes
-    // in compiler and/or library.
-    if config.download_rustc_commit.is_some() {
-        let mut paths = vec!["compiler"];
-
-        // Handle library tree the same way as in `Config::download_ci_rustc_commit`.
-        if builder.config.is_running_on_ci {
-            paths.push("library");
-        }
-
-        let has_changes = config.has_changes_from_upstream(&paths);
-
-        assert!(
-            !has_changes,
-            "CI-rustc can't be used with 'if-unchanged' while there are changes in compiler and/or library."
-        );
-    }
+    )
 }
 
 mod defaults {
diff --git a/src/bootstrap/src/utils/tests/git.rs b/src/bootstrap/src/utils/tests/git.rs
index 59581dd9c37b..f14af5f17fdb 100644
--- a/src/bootstrap/src/utils/tests/git.rs
+++ b/src/bootstrap/src/utils/tests/git.rs
@@ -81,13 +81,17 @@ pub fn merge(&self, branch: &str, author: &str) {
     }
 
     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 {