devserver: skip unlink when possible

[dmiller-figma]

Without this change we incur the cost of an extra unnecessary syscall on every file we need to sync. In my testing this didn't make a perceivable difference with small sets of changed files, however it could make a difference on large ones.

This change works just fine on Linux. However, on macOS you get a permission error if you try to copy over an existing file without grant_sandbox_write_permissions = True. So on macOS we only enable this optimization if grant_sandbox_write_permissions == True, otherwise we unlink the file like we did before.

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Changes are visible to end-users: no

Test plan

Existing tests

If it is possible to write a test that only runs on macOS, we could test that code path. However, I'm not sure how feasible that is.

[aspect-workflows]

Test

⚠️ Buildkite build #7580 failed.

Failed tests (1)

//docs:update_9_test [k8-fastbuild] 🔗

💡 To reproduce the test failures, run

bazel test //docs:update_9_test

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Test

e2e/bzlmod

All tests were cache hits

5 tests (100.0%) were fully cached saving 502ms.

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Test

e2e/gyp_no_install_script

All tests were cache hits

2 tests (100.0%) were fully cached saving 183ms.

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Test

e2e/js_image_oci

All tests were cache hits

1 test (100.0%) was fully cached saving 8s.

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Test

e2e/npm_link_package

All tests were cache hits

3 tests (100.0%) were fully cached saving 448ms.

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Test

e2e/npm_link_package-esm

All tests were cache hits

3 tests (100.0%) were fully cached saving 533ms.

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Test

e2e/npm_translate_lock

All tests were cache hits

1 test (100.0%) was fully cached saving 30ms.

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Test

e2e/npm_translate_lock_empty

All tests were cache hits

1 test (100.0%) was fully cached saving 30ms.

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Test

e2e/npm_translate_lock_multi

All tests were cache hits

2 tests (100.0%) were fully cached saving 268ms.

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Test

e2e/npm_translate_lock_partial_clone

All tests were cache hits

1 test (100.0%) was fully cached saving 31ms.

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Test

e2e/npm_translate_lock_replace_packages

All tests were cache hits

3 tests (100.0%) were fully cached saving 603ms.

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Test

e2e/npm_translate_lock_subdir_patch

All tests were cache hits

1 test (100.0%) was fully cached saving 98ms.

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Test

e2e/npm_translate_package_lock

All tests were cache hits

1 test (100.0%) was fully cached saving 31ms.

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Test

e2e/npm_translate_yarn_lock

All tests were cache hits

1 test (100.0%) was fully cached saving 31ms.

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Test

e2e/package_json_module

All tests were cache hits

1 test (100.0%) was fully cached saving 253ms.

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Test

e2e/pnpm_lockfiles

All tests were cache hits

42 tests (100.0%) were fully cached saving 3s.

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Test

e2e/pnpm_workspace

All tests were cache hits

10 tests (100.0%) were fully cached saving 2s.

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Test

e2e/pnpm_workspace_rerooted

All tests were cache hits

12 tests (100.0%) were fully cached saving 2s.

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Test

e2e/repo_mapping

All tests were cache hits

3 tests (100.0%) were fully cached saving 404ms.

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Test

e2e/rules_foo

All tests were cache hits

2 tests (100.0%) were fully cached saving 187ms.

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Test

e2e/runfiles

All tests were cache hits

1 test (100.0%) was fully cached saving 173ms.

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Test

e2e/vendored_node

All tests were cache hits

1 test (100.0%) was fully cached saving 99ms.

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Buildifier

Buildifier managed files require formatting

--- ./e2e/js_run_devserver/src/BUILD.bazel	2025-03-12 23:15:49.045607043 +0000
+++ /tmp/buildifier-tmp-1065325043	2025-03-12 23:16:19.457527224 +0000
@@ -120,8 +120,8 @@
         ":simple",
         ":web_files",
     ],
-    log_level = "debug",
     grant_sandbox_write_permissions = True,
+    log_level = "debug",
 )
 
 # Now the js_binary variant
@@ -140,9 +140,9 @@
     data = [
         ":web_files",
     ],
+    grant_sandbox_write_permissions = True,
     log_level = "debug",
     tool = ":simple_bin",
-    grant_sandbox_write_permissions = True,
 )
 
 # Intentionally a js_library and not a js_binary to test that transitive npm are

💡 Run the following to apply the suggested formatting fixes

bazel run //:buildifier

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Format

Formatting check has failed

💡 Some formatting failures can be fixed automatically by running the command below, while others may require manual fixes

bazel run //:format -- e2e/js_run_devserver/src/BUILD.bazel

ℹ️ A patch file containing the changes has been archived as an artifact of this build

[jbedard]

Don't we need to keep this when !grant_sandbox_write_permissions?

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