fix(builtin): don't restart npm_install rule just to look up a label (#2621)

Fixes #2620

Author: alexeagle

internal/npm_install/npm_install.bzl

@@ -473,6 +473,9 @@ cd /D "{root}" && "{npm}" {npm_args}
         env[env_key] = "1"
     env["BUILD_BAZEL_RULES_NODEJS_VERSION"] = VERSION
 
+    # NB: after running npm install, it's essential that we don't cause the repository rule to restart
+    # This means we must not reference any additional labels after this point.
+    # See https://github.com/bazelbuild/rules_nodejs/issues/2620
     repository_ctx.report_progress("Running npm install on %s" % repository_ctx.attr.package_json)
     result = repository_ctx.execute(
         [repository_ctx.path("_npm.cmd" if is_windows_host else "_npm.sh")],
@@ -484,16 +487,18 @@ cd /D "{root}" && "{npm}" {npm_args}
     if result.return_code:
         fail("npm_install failed: %s (%s)" % (result.stdout, result.stderr))
 
-    remove_npm_absolute_paths = Label("//third_party/github.com/juanjoDiaz/removeNPMAbsolutePaths:bin/removeNPMAbsolutePaths")
-
     # removeNPMAbsolutePaths is run on node_modules after npm install as the package.json files
     # generated by npm are non-deterministic. They contain absolute install paths and other private
     # information fields starting with "_". removeNPMAbsolutePaths removes all fields starting with "_".
+    fix_absolute_paths_cmd = [
+        node,
+        repository_ctx.path(repository_ctx.attr._remove_npm_absolute_paths),
+        root + "/node_modules",
+    ]
+
     if not repository_ctx.attr.quiet:
-        print([node, repository_ctx.path(remove_npm_absolute_paths), root + "/node_modules"])
-    result = repository_ctx.execute(
-        [node, repository_ctx.path(remove_npm_absolute_paths), root + "/node_modules"],
-    )
+        print(fix_absolute_paths_cmd)
+    result = repository_ctx.execute(fix_absolute_paths_cmd)
 
     if result.return_code:
         fail("remove_npm_absolute_paths failed: %s (%s)" % (result.stdout, result.stderr))
@@ -526,6 +531,7 @@ See npm CLI docs https://docs.npmjs.com/cli/install.html for complete list of su
             mandatory = True,
             allow_single_file = True,
         ),
+        "_remove_npm_absolute_paths": attr.label(default = Label("//third_party/github.com/juanjoDiaz/removeNPMAbsolutePaths:bin/removeNPMAbsolutePaths")),
     }),
     doc = """Runs npm install during workspace setup.