src/test/java/com/google/devtools/build/lib/packages/NativeExistingRulesTest.java

// Copyright 2021 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.devtools.build.lib.packages;

import static com.google.common.truth.Truth.assertThat;

import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
import java.util.HashMap;
import java.util.Map;
import net.starlark.java.annot.Param;
import net.starlark.java.annot.StarlarkBuiltin;
import net.starlark.java.annot.StarlarkMethod;
import net.starlark.java.eval.Dict;
import net.starlark.java.eval.Starlark;
import net.starlark.java.eval.StarlarkInt;
import net.starlark.java.eval.StarlarkList;
import net.starlark.java.eval.StarlarkValue;
import net.starlark.java.eval.Tuple;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/**
 * Tests for {@code native.existing_rule} and {@code native.existing_rules} functions.
 *
 * <p>This class covers the legacy behavior where the {@code
 * --incompatible_existing_rules_immutable_view} flag is disabled. The enabled case is covered by
 * the subclass, {@link WithImmutableView}.
 */
@RunWith(JUnit4.class)
public class NativeExistingRulesTest extends BuildViewTestCase {
  private TestStarlarkBuiltin testStarlarkBuiltin; // initialized by createRuleClassProvider()

  // Intended to be overridden by this test case's subclasses. Note that overriding of JUnit's
  // @Before methods is not recommended.
  protected void setupOptions() throws Exception {
    // --noincompatible_existing_rules_immutable_view is the default; set it explicitly for clarity.
    setBuildLanguageOptions("--noincompatible_existing_rules_immutable_view");
  }

  @Before
  public final void setUp() throws Exception {
    setupOptions();
  }

  @StarlarkBuiltin(name = "test")
  private static final class TestStarlarkBuiltin implements StarlarkValue {

    private final Map<String, Object> saved = new HashMap<>();

    @StarlarkMethod(
        name = "save",
        parameters = {
          @Param(name = "name", doc = "Name under which to save the value"),
          @Param(name = "value", doc = "Value to save")
        },
        doc = "Saves a Starlark value for testing from Java")
    public synchronized void save(String name, Object value) {
      saved.put(name, value);
    }
  }

  @Override
  protected ConfiguredRuleClassProvider createRuleClassProvider() {
    ConfiguredRuleClassProvider.Builder builder = new ConfiguredRuleClassProvider.Builder();
    TestRuleClassProvider.addStandardRules(builder);
    testStarlarkBuiltin = new TestStarlarkBuiltin();
    builder.addBzlToplevel("test", testStarlarkBuiltin);
    return builder.build();
  }

  private Object getSaved(String name) {
    return testStarlarkBuiltin.saved.get(name);
  }

  @Test
  public void existingRule_handlesSelect() throws Exception {
    scratch.file("test/starlark/BUILD");
    scratch.file(
        "test/starlark/rulestr.bzl",
        """
        def rule_dict(name):
            return native.existing_rule(name)
        """);

    scratch.file(
        "test/getrule/BUILD",
        """
        load("//test/starlark:rulestr.bzl", "rule_dict")

        cc_library(
            name = "x",
            srcs = select({"//conditions:default": []}),
        )

        rule_dict("x")
        """);

    // Parse the BUILD file, to make sure select() makes it out of native.existing_rule().
    assertThat(getConfiguredTarget("//test/getrule:x")).isNotNull();
  }

  @Test
  public void existingRule_returnsNone() throws Exception {
    scratch.file(
        "test/rulestr.bzl",
        """
        def test_rule(name, x):
            print(native.existing_rule(x))
            if native.existing_rule(x) == None:
                native.cc_library(name = name)
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:rulestr.bzl", "test_rule")

        test_rule("a", "does not exist")

        test_rule("b", "BUILD")
        """); // exists, but as a target and not a rule

    assertThat(getConfiguredTarget("//test:a")).isNotNull();
    assertThat(getConfiguredTarget("//test:b")).isNotNull();
  }

  @Test
  public void existingRule_roundTripsSelect() throws Exception {
    scratch.file(
        "test/existing_rule.bzl",
        """
        def macro():
            s = select({"//foo": ["//bar"]})
            print("Passed: " + repr(s))
            native.cc_library(name = "x", srcs = s)
            print("Returned: " + repr(native.existing_rule("x")["srcs"]))

            # The value returned here should round-trip fine.
            native.cc_library(name = "y", srcs = native.existing_rule("x")["srcs"])
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:existing_rule.bzl", "macro")

        macro()

        cc_library(
            name = "a",
            srcs = [],
        )
        """);
    getConfiguredTarget("//test:a");
    assertContainsEvent("Passed: select({\"//foo\": [\"//bar\"]}");
    // The short labels are now in their canonical form, and the sequence is represented as
    // tuple instead of list, but the meaning is unchanged.
    assertContainsEvent("Returned: select({\"//foo:foo\": (\"//bar:bar\",)}");
  }

  @Test
  public void existingRule_shortensLabelsInSamePackage() throws Exception {
    scratch.file(
        "test/existing_rule.bzl",
        """
        def save_deps():
            r = native.existing_rule("b")
            test.save("r['deps']", r["deps"])
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:existing_rule.bzl", "save_deps")

        cc_library(
            name = "a",
            srcs = [],
        )

        cc_binary(
            name = "b",
            deps = ["//test:a"],
        )

        save_deps()
        """);
    getConfiguredTarget("//test:b");
    assertThat(Starlark.toIterable(getSaved("r['deps']")))
        .containsExactly(":a"); // as opposed to "//test:a"
  }

  @Test
  public void existingRules_findsRulesAndAttributes() throws Exception {
    scratch.file("test/BUILD");
    scratch.file("test/starlark/BUILD");
    scratch.file(
        "test/starlark/rulestr.bzl",
        """
        def rule_dict(name):
            return native.existing_rule(name)

        def rules_dict():
            return native.existing_rules()

        def nop(ctx):
            pass

        nop_rule = rule(attrs = {"x": attr.label()}, implementation = nop)

        def test_save(name, value):
            test.save(name, value)
        """);

    scratch.file(
        "test/getrule/BUILD",
        """
        load("//test/starlark:rulestr.bzl", "nop_rule", "rule_dict", "rules_dict", "test_save")

        genrule(
            name = "a",
            outs = ["a.txt"],
            cmd = "touch $@",
            licenses = ["notice"],
            output_to_bindir = False,
            tools = ["//test:bla"],
        )

        nop_rule(
            name = "c",
            x = ":a",
        )

        rlist = rules_dict()

        test_save(
            "all_str",
            [
                rlist["a"]["kind"],
                rlist["a"]["name"],
                rlist["c"]["kind"],
                rlist["c"]["name"],
            ],
        )

        adict = rule_dict("a")

        cdict = rule_dict("c")

        test_save(
            "a_str",
            [
                adict["kind"],
                adict["name"],
                adict["outs"][0],
                adict["tools"][0],
            ],
        )

        test_save(
            "c_str",
            [
                cdict["kind"],
                cdict["name"],
                cdict["x"],
            ],
        )

        test_save(
            "adict.keys()",
            adict.keys(),
        )
        """);

    getConfiguredTarget("//test/getrule:BUILD");
    assertThat(Starlark.toIterable(getSaved("all_str")))
        .containsExactly("genrule", "a", "nop_rule", "c")
        .inOrder();
    assertThat(Starlark.toIterable(getSaved("a_str")))
        .containsExactly("genrule", "a", ":a.txt", "//test:bla")
        .inOrder();
    assertThat(Starlark.toIterable(getSaved("c_str")))
        .containsExactly("nop_rule", "c", ":a")
        .inOrder();
    assertThat(Starlark.toIterable(getSaved("adict.keys()")))
        .containsAtLeast(
            "name",
            "visibility",
            "transitive_configs",
            "tags",
            "generator_name",
            "generator_function",
            "generator_location",
            "features",
            "compatible_with",
            "target_compatible_with",
            "restricted_to",
            "srcs",
            "tools",
            "toolchains",
            "outs",
            "cmd",
            "output_to_bindir",
            "local",
            "message",
            "executable",
            "stamp",
            "heuristic_label_expansion",
            "kind");
  }

  @Test
  public void existingRule_ignoresHiddenAttributes() throws Exception {
    scratch.file(
        "test/inc.bzl",
        """
        def _check_hidden_attr_exists(ctx):
            if ctx.attr._hidden_attr != "hidden_val":
                fail('ctx.attr._hidden_attr != "hidden_val"')
            pass

        my_rule = rule(
            attrs = {
                "_hidden_attr": attr.string(default = "hidden_val"),
                "normal_attr": attr.string(default = "normal_val"),
            },
            implementation = _check_hidden_attr_exists,
        )

        def f():
            my_rule(name = "rulename")
            r = native.existing_rule("rulename")
            test.save("r.keys()", r.keys())
            test.save("r.values()", r.values())
            test.save('"_hidden_attr" in r', "_hidden_attr" in r)
        """);
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);

    assertThat(getConfiguredTarget("//test:rulename")).isNotNull();
    assertThat(Starlark.toIterable(getSaved("r.keys()")))
        .containsAtLeast("name", "kind", "normal_attr");
    assertThat(Starlark.toIterable(getSaved("r.keys()"))).doesNotContain("_hidden_attr");
    assertThat(Starlark.toIterable(getSaved("r.values()")))
        .containsAtLeast("rulename", "my_rule", "normal_val");
    assertThat(Starlark.toIterable(getSaved("r.values()"))).doesNotContain("hidden_val");
    assertThat((Boolean) getSaved("\"_hidden_attr\" in r")).isFalse();
  }

  @Test
  public void existingRule_returnsObjectWithCorrectMutability() throws Exception {
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);
    scratch.file(
        "test/inc.bzl",
        """
        def f():
            native.config_setting(name = "x", define_values = {"key": "value"})
            r = native.existing_rule("x")
            r["no_such_attribute"] = "foo"
            r["define_values"]["key"] = 123
        """); // mutate the dict

    assertThat(getConfiguredTarget("//test:BUILD")).isNotNull(); // no error on mutation
  }

  @Test
  public void existingRule_returnsDictLikeObject() throws Exception {
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);
    scratch.file(
        "test/inc.bzl",
        """
        def f():
            native.config_setting(name = "x", define_values = {"key": "value"})
            r = native.existing_rule("x")
            print("r == %s" % repr(r))
            test.save("[key for key in r]", [key for key in r])
            test.save("list(r)", list(r))
            test.save("r.keys()", r.keys())
            test.save("r.values()", r.values())
            test.save("r.items()", r.items())
            test.save("r['define_values']", r["define_values"])
            test.save("r.get('define_values', 123)", r.get("define_values", 123))
            test.save("r.get('invalid_attr', 123)", r.get("invalid_attr", 123))
            test.save("'define_values' in r", "define_values" in r)
            test.save("'invalid_attr' in r", "invalid_attr" in r)
        """);

    Dict<?, ?> expectedDefineValues = Dict.builder().put("key", "value").buildImmutable();
    assertThat(getConfiguredTarget("//test:BUILD")).isNotNull(); // no error
    assertThat(Starlark.toIterable(getSaved("[key for key in r]")))
        .containsAtLeast("define_values", "name", "kind");
    assertThat(Starlark.toIterable(getSaved("list(r)")))
        .containsAtLeast("define_values", "name", "kind");
    assertThat(Starlark.toIterable(getSaved("r.keys()")))
        .containsAtLeast("define_values", "name", "kind");
    assertThat(Starlark.toIterable(getSaved("r.values()")))
        .containsAtLeast(expectedDefineValues, "x", "config_setting");
    assertThat(Starlark.toIterable(getSaved("r.items()")))
        .containsAtLeast(
            Tuple.of("define_values", expectedDefineValues),
            Tuple.of("name", "x"),
            Tuple.of("kind", "config_setting"));
    assertThat(getSaved("r['define_values']")).isEqualTo(expectedDefineValues);
    assertThat(getSaved("r.get('define_values', 123)")).isEqualTo(expectedDefineValues);
    assertThat(getSaved("r.get('invalid_attr', 123)")).isEqualTo(StarlarkInt.of(123));
    assertThat(getSaved("'define_values' in r")).isEqualTo(true);
    assertThat(getSaved("'invalid_attr' in r")).isEqualTo(false);
  }

  @Test
  public void existingRule_asDictArgument() throws Exception {
    scratch.file(
        "test/test.bzl",
        """
        def save_as_dict(r):
            test.save("type(dict(r))", type(dict(r)))
            test.save('dict(r)["name"]', dict(r)["name"])
            test.save('dict(r)["kind"]', dict(r)["kind"])
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "save_as_dict")

        cc_library(
            name = "rulename",
        )

        save_as_dict(existing_rule("rulename"))
        """);
    getConfiguredTarget("//test:rulename");
    assertThat(getSaved("type(dict(r))")).isEqualTo("dict");
    assertThat(getSaved("dict(r)[\"name\"]")).isEqualTo("rulename");
    assertThat(getSaved("dict(r)[\"kind\"]")).isEqualTo("cc_library");
  }

  @Test
  public void existingRule_asDictUpdateArgument() throws Exception {
    // We do not test `existing_rule(r).update({...})` because `existing_rule(r)` may be immutable
    // (as verified by other test cases).
    scratch.file(
        "test/test.bzl",
        """
        def save_as_updated_dict(r):
            updated_dict = {"name": "dictname", "dictkey": 1}
            updated_dict.update(r)
            test.save('updated_dict["name"]', updated_dict["name"])
            test.save('updated_dict["kind"]', updated_dict["kind"])
            test.save('updated_dict["dictkey"]', updated_dict["dictkey"])
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "save_as_updated_dict")

        cc_library(
            name = "rulename",
        )

        save_as_updated_dict(existing_rule("rulename"))
        """);
    getConfiguredTarget("//test:rulename");
    assertThat(getSaved("updated_dict[\"name\"]")).isEqualTo("rulename");
    assertThat(getSaved("updated_dict[\"kind\"]")).isEqualTo("cc_library");
    assertThat(getSaved("updated_dict[\"dictkey\"]")).isEqualTo(StarlarkInt.of(1));
  }

  @Test
  public void existingRule_unionableWithDict() throws Exception {
    scratch.file(
        "test/test.bzl",
        """
        def save_as_union(dict_val, r):
            test.save("dict_val | r", dict_val | r)
            test.save("r | dict_val", r | dict_val)
            dict_val |= r
            test.save("dict_val |= r", dict_val)
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "save_as_union")

        cc_library(
            name = "rulename",
        )

        save_as_union(
            {
                "name": "dictname",
                "dictkey": 1,
            },
            existing_rule("rulename"),
        )
        """);
    getConfiguredTarget("//test:rulename");
    Map<String, Object> unionDictWithExistingRule =
        Dict.cast(getSaved("dict_val | r"), String.class, Object.class, "dict_val | r");
    assertThat(unionDictWithExistingRule)
        .containsAtLeast("name", "rulename", "dictkey", StarlarkInt.of(1), "kind", "cc_library");
    Map<String, Object> unionExistingRuleWithDict =
        Dict.cast(getSaved("r | dict_val"), String.class, Object.class, "r | dict_val");
    assertThat(unionExistingRuleWithDict)
        .containsAtLeast("name", "dictname", "dictkey", StarlarkInt.of(1), "kind", "cc_library");
    Map<String, Object> inPlaceUnionDictWithExistingRule =
        Dict.cast(getSaved("dict_val |= r"), String.class, Object.class, "dict_val | r");
    assertThat(inPlaceUnionDictWithExistingRule)
        .containsAtLeast("name", "rulename", "dictkey", StarlarkInt.of(1), "kind", "cc_library");
  }

  @Test
  public void existingRule_asKwargs() throws Exception {
    scratch.file(
        "test/test.bzl",
        """
        def save_kwargs(**kwargs):
            test.save('kwargs["name"]', kwargs["name"])
            test.save('kwargs["kind"]', kwargs["kind"])

        def save_kwargs_of_existing_rule(name):
            save_kwargs(**native.existing_rule(name))
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "save_kwargs_of_existing_rule")

        cc_library(
            name = "rulename",
        )

        save_kwargs_of_existing_rule("rulename")
        """);
    getConfiguredTarget("//test:rulename");
    assertThat(getSaved("kwargs[\"name\"]")).isEqualTo("rulename");
    assertThat(getSaved("kwargs[\"kind\"]")).isEqualTo("cc_library");
  }

  // Regression test for https://github.com/bazelbuild/bazel/issues/16256
  @Test
  public void existingRule_encodesToJson() throws Exception {
    // We need a Starlark rule - native rules can have attribute values that the json encoder
    // doesn't handle.
    scratch.file(
        "test/test.bzl",
        """
        def _dummy_impl(ctx):
            pass

        test_library = rule(
            implementation = _dummy_impl,
            attrs = {"srcs": attr.label_list(allow_files = True)},
        )

        # TODO(b/249397668): simplifying this to `json_encode = json.encode` etc. causes a
        # NoCodecException. Need to investigate.
        def json_encode(value):
            return json.encode(value)

        def json_decode(text):
            return json.decode(text)

        def save(name, object):
            test.save(name, object)
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "json_decode", "json_encode", "save", "test_library")

        test_library(
            name = "foo",
            srcs = ["foo.cc"],
        )

        save(
            "foo",
            json_decode(json_encode(existing_rule("foo"))),
        )
        """);
    scratch.file("test/foo.cc");
    getConfiguredTarget("//test:foo");
    // We test a subset of attributes after an encode-decode round trip because the rule also has
    // default attributes with default values, which will get encoded to json and which will change
    // whenever default attributes get introduced, making string comparison of encoded json fragile.
    Map<String, Object> jsonRoundTripValue =
        Dict.cast(
            getSaved("foo"), String.class, Object.class, "json round trip of existing_rule('foo')");
    assertThat(jsonRoundTripValue)
        .containsAtLeast(
            "name", "foo", "kind", "test_library", "srcs", StarlarkList.immutableOf(":foo.cc"));
  }

  @Test
  public void existingRules_returnsObjectWithCorrectMutability() throws Exception {
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);
    scratch.file(
        "test/inc.bzl",
        """
        def f():
            native.config_setting(name = "x", define_values = {"key": "value"})
            rs = native.existing_rules()
            rs["no_such_rule"] = {"name": "no_such_rule", "kind": "config_setting"}
        """); // mutate

    assertThat(getConfiguredTarget("//test:BUILD")).isNotNull(); // no error on mutation
  }

  @Test
  public void existingRules_returnsDictLikeObject() throws Exception {
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);
    scratch.file(
        "test/inc.bzl", //
        "def f():",
        "  native.config_setting(name='x', define_values={'key_x': 'value_x'})",
        "  native.config_setting(name='y', define_values={'key_y': 'value_y'})",
        "  rs = native.existing_rules()",
        "  print('rs == %s' % repr(rs))",
        "  test.save('[key for key in rs]', [key for key in rs])",
        "  test.save('list(rs)', list(rs))",
        "  test.save('rs.keys()', rs.keys())",
        "  test.save(\"[v['name'] for v in rs.values()]\", [v['name'] for v in rs.values()])",
        "  test.save(\"[(i[0], i[1]['name']) for i in rs.items()]\", [(i[0], i[1]['name']) for i in"
            + " rs.items()])",
        "  test.save(\"rs['x']['define_values']\", rs['x']['define_values'])",
        "  test.save(\"rs.get('x', {'name': 'z'})['name']\", rs.get('x', {'name': 'z'})['name'])",
        "  test.save(\"rs.get('invalid_rule', {'name': 'invalid_rule'})\", rs.get('invalid_rule',"
            + " {'name': 'invalid_rule'}))",
        "  test.save(\"'x' in rs\", 'x' in rs)",
        "  test.save(\"'invalid_rule' in rs\", 'invalid_rule' in rs)");

    assertThat(getConfiguredTarget("//test:BUILD")).isNotNull(); // no error
    assertThat(Starlark.toIterable(getSaved("[key for key in rs]"))).containsExactly("x", "y");
    assertThat(Starlark.toIterable(getSaved("list(rs)"))).containsExactly("x", "y");
    assertThat(Starlark.toIterable(getSaved("rs.keys()"))).containsExactly("x", "y");
    assertThat(Starlark.toIterable(getSaved("[v['name'] for v in rs.values()]")))
        .containsExactly("x", "y");
    assertThat(Starlark.toIterable(getSaved("[(i[0], i[1]['name']) for i in rs.items()]")))
        .containsExactly(Tuple.of("x", "x"), Tuple.of("y", "y"));
    assertThat(getSaved("rs['x']['define_values']"))
        .isEqualTo(Dict.builder().put("key_x", "value_x").buildImmutable());
    assertThat(getSaved("rs.get('x', {'name': 'z'})['name']")).isEqualTo("x");
    assertThat(getSaved("rs.get('invalid_rule', {'name': 'invalid_rule'})"))
        .isEqualTo(Dict.builder().put("name", "invalid_rule").buildImmutable());
    assertThat(getSaved("'x' in rs")).isEqualTo(true);
    assertThat(getSaved("'invalid_rule' in rs")).isEqualTo(false);
  }

  @Test
  public void existingRules_returnsSnapshotOfOnlyRulesInstantiatedUpToThatPoint() throws Exception {
    scratch.file(
        "test/BUILD",
        """
        load("inc.bzl", "f")

        f()
        """);
    scratch.file(
        "test/inc.bzl",
        """
        def f():
            native.config_setting(name = "x", define_values = {"key_x": "value_x"})
            rs1 = native.existing_rules()
            native.config_setting(name = "y", define_values = {"key_y": "value_y"})
            rs2 = native.existing_rules()
            native.config_setting(name = "z", define_values = {"key_z": "value_z"})
            rs3 = native.existing_rules()
            test.save("rs1.keys()", rs1.keys())
            test.save("rs2.keys()", rs2.keys())
            test.save("rs3.keys()", rs3.keys())
        """);

    assertThat(getConfiguredTarget("//test:BUILD")).isNotNull(); // no error
    assertThat(Starlark.toIterable(getSaved("rs1.keys()"))).containsExactly("x");
    assertThat(Starlark.toIterable(getSaved("rs2.keys()"))).containsExactly("x", "y");
    assertThat(Starlark.toIterable(getSaved("rs3.keys()"))).containsExactly("x", "y", "z");
  }

  // Regression test for https://github.com/bazelbuild/bazel/issues/16256
  @Test
  public void existingRules_encodeToJson() throws Exception {
    // We need a Starlark rule - native rules can have attribute values that the json encoder
    // doesn't handle.
    scratch.file(
        "test/test.bzl",
        """
        def _dummy_impl(ctx):
            pass

        test_library = rule(
            implementation = _dummy_impl,
            attrs = {"srcs": attr.label_list(allow_files = True)},
        )

        # TODO(b/249397668): simplifying this to `json_encode = json.encode` etc. causes a
        # NoCodecException. Need to investigate.
        def json_encode(value):
            return json.encode(value)

        def json_decode(text):
            return json.decode(text)

        def save(name, object):
            test.save(name, object)
        """);
    scratch.file(
        "test/BUILD",
        """
        load("//test:test.bzl", "json_decode", "json_encode", "save", "test_library")

        test_library(
            name = "foo",
            srcs = ["foo.cc"],
        )

        test_library(
            name = "bar",
            srcs = ["bar.cc"],
        )

        save(
            "rules",
            json_decode(json_encode(existing_rules())),
        )
        """);
    scratch.file("test/foo.cc");
    getConfiguredTarget("//test:bar");
    // We test a subset of attributes after an encode-decode round trip because the rule also has
    // default attributes with default values, which will get encoded to json and which will change
    // whenever default attributes get introduced, making string comparison of encoded json fragile.
    Dict<String, Object> jsonRoundTripRulesValue =
        Dict.cast(
            getSaved("rules"), String.class, Object.class, "json round trip of `existing_rules()`");
    assertThat(jsonRoundTripRulesValue.keySet()).containsExactly("foo", "bar");
    Map<String, Object> jsonRoundTripFooValue =
        Dict.cast(
            jsonRoundTripRulesValue.get("foo"),
            String.class,
            Object.class,
            "json round trip of `existing_rule('foo')`");
    assertThat(jsonRoundTripFooValue)
        .containsAtLeast(
            "name", "foo", "kind", "test_library", "srcs", StarlarkList.immutableOf(":foo.cc"));
    Map<String, Object> jsonRoundTripBarValue =
        Dict.cast(
            jsonRoundTripRulesValue.get("bar"),
            String.class,
            Object.class,
            "json round trip of `existing_rule('bar')`");
    assertThat(jsonRoundTripBarValue)
        .containsAtLeast(
            "name", "bar", "kind", "test_library", "srcs", StarlarkList.immutableOf(":bar.cc"));
  }

  /**
   * Tests for {@code native.existing_rule} and {@code native.existing_rules} Starlark functions
   * with the {@code --incompatible_existing_rules_immutable_view} flag set.
   */
  @RunWith(JUnit4.class)
  public static final class WithImmutableView extends NativeExistingRulesTest {

    @Override
    protected void setupOptions() throws Exception {
      setBuildLanguageOptions("--incompatible_existing_rules_immutable_view");
    }

    @Test
    @Override
    public void existingRule_returnsObjectWithCorrectMutability() throws Exception {
      scratch.file(
          "test/BUILD",
          """
          load("inc.bzl", "f")

          f()
          """);
      scratch.file(
          "test/inc.bzl",
          """
          def f():
              native.config_setting(name = "x", define_values = {"key": "value"})
              r = native.existing_rule("x")
              r["no_such_attribute"] = 123
          """); // mutate the view

      reporter.removeHandler(failFastHandler);
      assertThat(getConfiguredTarget("//test:BUILD")).isNull(); // mutation fails
      assertContainsEvent("can only assign an element in a dictionary or a list");
    }

    @Test
    @Override
    public void existingRules_returnsObjectWithCorrectMutability() throws Exception {
      scratch.file(
          "test/BUILD",
          """
          load("inc.bzl", "f")

          f()
          """);
      scratch.file(
          "test/inc.bzl",
          """
          def f():
              native.config_setting(name = "x", define_values = {"key": "value"})
              rs = native.existing_rules()
              rs["no_such_rule"] = {"name": "no_such_rule", "kind": "config_setting"}
          """); // mutate

      reporter.removeHandler(failFastHandler);
      assertThat(getConfiguredTarget("//test:BUILD")).isNull(); // mutation fails
      assertContainsEvent("can only assign an element in a dictionary or a list");
    }

    @Test
    public void existingRules_returnsDeeplyImmutableView() throws Exception {
      scratch.file(
          "test/BUILD",
          """
          load("inc.bzl", "f")

          f()
          """);
      scratch.file(
          "test/inc.bzl",
          """
          def f():
              native.config_setting(name = "x", define_values = {"key": "value"})
              rs = native.existing_rules()
              rs["x"]["define_values"]["key"] = 123
          """); // mutate an attribute value within the view

      reporter.removeHandler(failFastHandler);
      assertThat(getConfiguredTarget("//test:BUILD")).isNull();
      assertContainsEvent("trying to mutate a frozen dict value");
    }
  }
}