From da7c264e4a1ad03fa373dabfcc08251ed1426819 Mon Sep 17 00:00:00 2001
From: Jason Bedard <jason+github@jbedard.ca>
Date: Fri, 7 Jun 2024 15:15:44 -0700
Subject: [PATCH] perf(npm): avoid large array concatenation

---
 js/private/js_helpers.bzl   | 24 +++++++++++++++++-------
 npm/private/npm_package.bzl | 15 ++++++++++-----
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/js/private/js_helpers.bzl b/js/private/js_helpers.bzl
index c3a70ef8c4..359e6f8ef8 100644
--- a/js/private/js_helpers.bzl
+++ b/js/private/js_helpers.bzl
@@ -49,11 +49,18 @@ def gather_npm_sources(srcs, deps):
         Depset of npm sources
     """
 
-    return depset(transitive = [
-        target[JsInfo].npm_sources
-        for target in srcs + deps
-        if JsInfo in target
-    ])
+    transitive = []
+
+    # Duplicate loops to avoid src + deps concat
+    for target in srcs:
+        if JsInfo in target:
+            transitive.append(target[JsInfo].npm_sources)
+
+    for target in deps:
+        if JsInfo in target:
+            transitive.append(target[JsInfo].npm_sources)
+
+    return depset([], transitive = transitive)
 
 def gather_npm_package_store_infos(targets):
     """Gathers NpmPackageStoreInfo providers from the list of targets
@@ -182,9 +189,12 @@ def gather_runfiles(
     for target in data:
         transitive_files_depsets.append(target[DefaultInfo].files)
 
+    # Avoid concatenating more then once
+    data_deps = data + deps
+
     # Gather files from JsInfo providers of data & deps
     transitive_files_depsets.append(gather_files_from_js_infos(
-        targets = data + deps,
+        targets = data_deps,
         include_sources = include_sources,
         include_types = include_types,
         include_transitive_sources = include_transitive_sources,
@@ -209,7 +219,7 @@ def gather_runfiles(
         transitive_files = depset(transitive = transitive_files_depsets),
     ).merge_all([
         target[DefaultInfo].default_runfiles
-        for target in data + deps
+        for target in data_deps
     ])
 
 LOG_LEVELS = {
diff --git a/npm/private/npm_package.bzl b/npm/private/npm_package.bzl
index 4620478b4b..419959fbc0 100644
--- a/npm/private/npm_package.bzl
+++ b/npm/private/npm_package.bzl
@@ -16,6 +16,7 @@ load("@bazel_skylib//lib:dicts.bzl", "dicts")
 load("@bazel_skylib//lib:versions.bzl", "versions")
 load("//js:defs.bzl", "js_binary")
 load("//js:libs.bzl", "js_lib_helpers")
+load("//js:providers.bzl", "JsInfo")
 load(":npm_package_info.bzl", "NpmPackageInfo")
 
 # Pull in all copy_to_directory attributes except for exclude_prefixes
@@ -68,10 +69,14 @@ def _npm_package_files_impl(ctx):
 def _npm_package_impl(ctx):
     dst = ctx.actions.declare_directory(ctx.attr.out if ctx.attr.out else ctx.attr.name)
 
-    # forward all npm_package_store_infos
-    npm_package_store_infos = js_lib_helpers.gather_npm_package_store_infos(
-        targets = ctx.attr.srcs + ctx.attr.data,
-    )
+    # forward all src+data npm_package_store_infos
+    npm_package_store_infos = []
+    for target in ctx.attr.srcs:
+        if JsInfo in target:
+            npm_package_store_infos.append(target[JsInfo].npm_package_store_infos)
+    for target in ctx.attr.data:
+        if JsInfo in target:
+            npm_package_store_infos.append(target[JsInfo].npm_package_store_infos)
 
     copy_to_directory_bin_action(
         ctx,
@@ -103,7 +108,7 @@ def _npm_package_impl(ctx):
             package = ctx.attr.package,
             version = ctx.attr.version,
             src = dst,
-            npm_package_store_infos = npm_package_store_infos,
+            npm_package_store_infos = depset(transitive = npm_package_store_infos),
         ),
     ]