Do not watch .netrc in read_netrc

Modifying auth information should not result in a repo rule being reevaluated after a successful evaluation. This regressed in a5376aa.

Fixes bazelbuild#22118

Closes bazelbuild#22125.

PiperOrigin-RevId: 629182408
Change-Id: I0c553e9ded72230b647a37203d51ba779976d7fc

src/test/shell/bazel/starlark_repository_test.sh

@@ -1963,6 +1963,7 @@ EOF
   cat > def.bzl <<'EOF'
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "read_netrc", "use_netrc")
 def _impl(ctx):
+  print("authrepo is being evaluated")
   rc = read_netrc(ctx, ctx.attr.path)
   auth = use_netrc(rc, ctx.attr.urls, {"oauthlife.com": "Bearer <password>",})
   ctx.file("data.bzl", "auth = %s" % (auth,))
@@ -2044,9 +2045,16 @@ genrule(
   cmd = "echo %s > $@" % (check_equal_expected(),)
 )
 EOF
-  bazel build //:check_expected
+  bazel build //:check_expected &> $TEST_log || fail "Expected success"
   grep 'OK' `bazel info bazel-bin`/check_expected.txt \
        || fail "Authentication merged incorrectly"
+  expect_log "authrepo is being evaluated"
+
+  echo "modified" > .netrc
+  bazel build //:check_expected &> $TEST_log || fail "Expected success"
+  grep 'OK' `bazel info bazel-bin`/check_expected.txt \
+       || fail "Authentication information should not have been reevaluated"
+  expect_not_log "authrepo is being evaluated"
 }
 
 function test_disallow_unverified_http() {

tools/build_defs/repo/utils.bzl

@@ -251,7 +251,10 @@ def read_netrc(ctx, filename):
       dict mapping a machine names to a dict with the information provided
       about them
     """
-    contents = ctx.read(filename)
+
+    # Do not cause the repo rule to rerun due to changes to auth info when it is
+    # successful. Failures are not cached.
+    contents = ctx.read(filename, watch = "no")
     return parse_netrc(contents, filename)
 
 def parse_netrc(contents, filename = None):