Add support for snapshot tests with insta

Author: Kobzol

src/bootstrap/Cargo.lock

@@ -44,6 +44,7 @@ dependencies = [
  "fd-lock",
  "home",
  "ignore",
+ "insta",
  "junction",
  "libc",
  "object",
@@ -158,6 +159,18 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "console"
+version = "0.15.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "054ccb5b10f9f2cbf51eb355ca1d05c2d279ce1804688d0db74b4733a5aeafd8"
+dependencies = [
+ "encode_unicode",
+ "libc",
+ "once_cell",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.15"
@@ -218,6 +231,12 @@ dependencies = [
  "crypto-common",
 ]
 
+[[package]]
+name = "encode_unicode"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34aa73646ffb006b8f5147f3dc182bd4bcb190227ce861fc4a4844bf8e3cb2c0"
+
 [[package]]
 name = "errno"
 version = "0.3.11"
@@ -323,6 +342,17 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "insta"
+version = "1.43.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "154934ea70c58054b556dd430b99a98c2a7ff5309ac9891597e339b5c28f4371"
+dependencies = [
+ "console",
+ "once_cell",
+ "similar",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.11"
@@ -675,6 +705,12 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
 
+[[package]]
+name = "similar"
+version = "2.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbbb5d9659141646ae647b42fe094daf6c6192d1620870b449d9557f748b2daa"
+
 [[package]]
 name = "smallvec"
 version = "1.13.2"

src/bootstrap/Cargo.toml

@@ -84,6 +84,7 @@ features = [
 [dev-dependencies]
 pretty_assertions = "1.4"
 tempfile = "3.15.0"
+insta = "1.43"
 
 # We care a lot about bootstrap's compile times, so don't include debuginfo for
 # dependencies, only bootstrap itself.

src/bootstrap/README.md

@@ -200,6 +200,10 @@ please file issues on the [Rust issue tracker][rust-issue-tracker].
 [rust-bootstrap-zulip]: https://rust-lang.zulipchat.com/#narrow/stream/t-infra.2Fbootstrap
 [rust-issue-tracker]: https://github.com/rust-lang/rust/issues
 
+## Testing
+
+To run bootstrap tests, execute `x test bootstrap`. If you want to bless snapshot tests, then install `cargo-insta` (`cargo install cargo-insta`) and then run `cargo insta review --manifest-path src/bootstrap/Cargo.toml`.
+
 ## Changelog
 
 Because we do not release bootstrap with versions, we also do not maintain CHANGELOG files. To

src/bootstrap/src/core/build_steps/test.rs

@@ -3059,6 +3059,8 @@ impl Step for Bootstrap {
         cargo
             .rustflag("-Cdebuginfo=2")
             .env("CARGO_TARGET_DIR", builder.out.join("bootstrap"))
+            // Needed for insta to correctly write pending snapshots to the right directories.
+            .env("INSTA_WORKSPACE_ROOT", &builder.src)
             .env("RUSTC_BOOTSTRAP", "1");
 
         // bootstrap tests are racy on directory creation so just run them one at a time.