fix(builtin): reduce linker debug string allocations (#3309)

fmeum · web-flow · commit fb2eeacf82d6 · 2022-02-02T10:22:25.000-08:00
Construct the formatted strings lazily to prevent allocating and
formatting a string for every transitive dependency.
diff --git a/internal/linker/link_node_modules.bzl b/internal/linker/link_node_modules.bzl
@@ -14,9 +14,9 @@ runtimes to locate all the first-party packages.
 load("//internal/providers:external_npm_package_info.bzl", "ExternalNpmPackageInfo")
 load("@rules_nodejs//nodejs:providers.bzl", "LinkablePackageInfo")
 
-def _debug(vars, *args):
+def _debug(vars, format, args_tuple):
     if "VERBOSE_LOGS" in vars.keys():
-        print("[link_node_modules.bzl]", *args)
+        print("[link_node_modules.bzl]", format % args_tuple)
 
 LinkerPackageMappingInfo = provider(
     doc = """Provider capturing package mappings for the linker to consume.""",
@@ -194,9 +194,9 @@ def _get_linker_package_mapping_info(target, ctx):
     # Look for LinkablePackageInfo mapping in this node
     # LinkablePackageInfo may be provided without a package_name so check for that case as well
     if not LinkablePackageInfo in target:
-        _debug(ctx.var, "No LinkablePackageInfo for", target.label)
+        _debug(ctx.var, "No LinkablePackageInfo for %s", (target.label))
     elif not target[LinkablePackageInfo].package_name:
-        _debug(ctx.var, "No package_name in LinkablePackageInfo for", target.label)
+        _debug(ctx.var, "No package_name in LinkablePackageInfo for %s", (target.label))
     else:
         linkable_package_info = target[LinkablePackageInfo]
         package_path = linkable_package_info.package_path if hasattr(linkable_package_info, "package_path") else ""
@@ -207,7 +207,7 @@ def _get_linker_package_mapping_info(target, ctx):
                 link_path = linkable_package_info.path,
             ),
         )
-        _debug(ctx.var, "target %s (package path: %s) adding module mapping %s: %s" % (
+        _debug(ctx.var, "target %s (package path: %s) adding module mapping %s: %s", (
             target.label,
             package_path,
             linkable_package_info.package_name,
