fix(examples): run jest updateSnapshot in the workspace (#3041)

Otherwise it creates snapshot files in the runfiles tree

examples/jest/jest.bzl

@@ -1,6 +1,7 @@
 "Shows how you might create a macro for the autogenerated Jest rule"
 
 load("@npm//jest-cli:index.bzl", "jest", _jest_test = "jest_test")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
 
 def jest_test(name, srcs, deps, jest_config, **kwargs):
     "A macro around the autogenerated jest_test rule"
@@ -22,10 +23,27 @@ def jest_test(name, srcs, deps, jest_config, **kwargs):
         **kwargs
     )
 
+    # Make sure the update command runs with a working directory in the workspace
+    # so that any created snapshot files are in the sources, not in the runfiles
+    write_file(
+        name = "chdir",
+        out = "chdir.js",
+        content = [
+            # cd /path/to/workspace
+            "process.chdir(process.env['BUILD_WORKSPACE_DIRECTORY'])",
+            # cd subdir/package
+            "process.chdir('%s')" % native.package_name() if native.package_name() else "",
+        ],
+    )
+
     # This rule is used specifically to update snapshots via `bazel run`
     jest(
         name = "%s.update" % name,
-        data = data,
-        templated_args = templated_args + ["-u"],
+        data = data + ["chdir.js"],
+        templated_args = templated_args + [
+            "--updateSnapshot",
+            "--runInBand",
+            "--node_options=--require=$(rootpath chdir.js)",
+        ],
         **kwargs
     )