feat: rust insta snapshot example

.github/workflows/ci.yaml

@@ -49,7 +49,7 @@ jobs:
       - uses: tj-actions/changed-files@48d8f15b2aaa3d255ca5af3eba4870f807ce6b3c  # v45
         with:
           # NB: this list must match all files that live within a nested Bazel module.
-          # Should match the /.bazelignore file as well.
+          # Should match the /REPO.bazel file as well.
           files: |
             angular-ngc/**
             jest/**
@@ -61,6 +61,7 @@ jobs:
             jest/**
             nestjs/**
             prisma/**
+            rust_insta_snapshot_test/**
             rules_nodejs_to_rules_js_migration/**
             ts_project_transpiler/**
           # Just print the top-level directory names

REPO.bazel

@@ -7,7 +7,9 @@ ignore_directories([
     "**/node_modules",
     "**/.pytest_cache",
     "**/__pycache__",
-    # Nested projects that should be moved into the root workspace:
+    # Nested modules.
+    # TODO(alexeagle): some of these should move to the root
+    # NB: when updating this list, also add to .github/workflows/ci.yaml
     "angular-ngc",
     "bzlmod",
     "check-npm-determinism",
@@ -21,6 +23,7 @@ ignore_directories([
     "oci_java_image",
     "prisma",
     "rules_nodejs_to_rules_js_migration",
+    "rust_insta_snapshot_test",
     "ts_project_transpiler",
     "vercel_pkg",
 ])

rust_insta_snapshot_test/.bazelversion

@@ -0,0 +1 @@
+8.5.0

rust_insta_snapshot_test/.gitignore

@@ -0,0 +1,2 @@
+bazel-*
+target

rust_insta_snapshot_test/BUILD.bazel

@@ -0,0 +1,11 @@
+load("//:defs.bzl", "rust_snapshot_test")
+
+rust_snapshot_test(
+    name = "test",
+    srcs = ["src/test.rs"],
+    crate_root = "src/test.rs",
+    snapshots_dir = "src/snapshots",
+    deps = [
+        "@crate_index//:insta",
+    ],
+)

rust_insta_snapshot_test/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "rust_insta_snapshot_test"
+version = "0.0.0"
+edition = "2024"
+publish = false
+
+[[test]]
+name = "test"
+path = "src/test.rs"
+
+[dependencies]
+insta = "1.46.0"

rust_insta_snapshot_test/MODULE.bazel

@@ -0,0 +1,48 @@
+"""bazelbuild/rules_rust - bzlmod example"""
+
+module(
+    name = "snapshot_test_example",
+    version = "0.0.0",
+)
+
+bazel_dep(name = "bazel_lib", version = "3.1.0")
+bazel_dep(name = "rules_rust", version = "0.68.1")
+bazel_dep(name = "rules_shell", version = "0.6.1")
+bazel_dep(name = "sed", version = "4.9.bcr.3")
+
+rust_host_tools = use_extension("@rules_rust//rust:extensions.bzl", "rust_host_tools")
+rust_host_tools.host_tools(
+    name = "rust_host_tools_nightly",
+    version = "nightly",
+)
+use_repo(
+    rust_host_tools,
+    "rust_host_tools_nightly",
+)
+
+crate = use_extension(
+    "@rules_rust//crate_universe:extensions.bzl",
+    "crate",
+)
+crate.from_cargo(
+    name = "crate_index",
+    cargo_lockfile = "//:Cargo.lock",
+    manifests = ["//:Cargo.toml"],
+)
+use_repo(crate, "crate_index")
+
+bindeps = use_extension("@rules_rust//crate_universe:extension.bzl", "crate")
+bindeps.spec(
+    artifact = "bin",
+    package = "cargo-insta",
+    version = "1.46.0",
+)
+bindeps.annotation(
+    crate = "cargo-insta",
+    gen_all_binaries = True,
+)
+bindeps.from_specs(
+    name = "bindeps",
+    host_tools = "@rust_host_tools_nightly",
+)
+use_repo(bindeps, "bindeps")

rust_insta_snapshot_test/README.md

@@ -0,0 +1,33 @@
+# insta snapshot tests
+
+An example for working with [insta](https://crates.io/crates/insta) snapshot tests under Bazel.
+
+The `rust_snapshot_test` macro creates a `rust_test` which is run as a build action to create snapshots in the output tree, along with a `diff_test` to check whether any snapshots need to be applied. The diff test outputs a commands to run to review or accept the snapshot changes.
+
+```starlark
+rust_snapshot_test(
+    name = "test",
+    snapshots_dir = "src/snapshots",
+    srcs = ["src/test.rs"],
+    crate_root = "src/test.rs",
+    deps = [
+        "@crate_index//:insta",
+    ],
+)
+```
+
+Snapshots can be interactively reviewed using insta and written back to the source tree. For example, the following command runs `cargo insta review`.
+
+```bash
+bazel run //:test_review
+```
+
+Or, to accept all snapshot changes without reviewing them:
+
+```bash
+bazel run //:test_accept
+```
+
+## Limitations
+
+* There isn't a way to remove unreferenced snapshots when reviewing, though this may be supported in the future (see https://github.com/mitsuhiko/insta/blob/3aa59d6f94d1b0c25d5953231019aa1eadbb4017/cargo-insta/src/cli.rs#L1079).