chore: define a local jsonnet_json_golden_test rule instead of using rules_jsonnet

Although rules_jsonnet is the appropriate Bazel module for external
Jsonnet users to use for their Jsonnet build actions, using it
internally within the jsonnet repo itself is actually a little difficult
as it creates a mutually recursive dependency.

Since the only thing it's being used for is the jsonnet_json_test rule,
and we have scripts to runs such tests anyway, it's relatively easy to
define our own jsonnet_json_golden_test rule and avoid the recursive
dependency.

Author: johnbartholomew

cpp/testdata/BUILD

@@ -1,40 +1,27 @@
-load(
-    "@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl",
-    "jsonnet_library",
-    "jsonnet_to_json_test",
-)
+load("//tools/build_defs:golden_test.bzl", "jsonnet_json_golden_test")
 
 package(default_visibility = ["//visibility:public"])
 
-jsonnet_to_json_test(
+jsonnet_json_golden_test(
     name = "example_test",
     src = "example.jsonnet",
     golden = "example_golden.json",
 )
 
-jsonnet_to_json_test(
+jsonnet_json_golden_test(
     name = "importing_test",
     src = "importing.jsonnet",
+    data = ["example.jsonnet"],
     golden = "importing_golden.json",
-    imports = ["."],
-    deps = [":testlib"],
 )
 
-jsonnet_to_json_test(
+jsonnet_json_golden_test(
     name = "invalid_test",
     src = "invalid.jsonnet",
-    error = 1,
+    expect_error = True,
     golden = "invalid.out",
 )
 
-jsonnet_library(
-    name = "testlib",
-    srcs = [
-        "example.jsonnet",
-        "importing.jsonnet",
-    ],
-)
-
 filegroup(
     name = "testdata",
     srcs = [

test_suite/BUILD

@@ -0,0 +1,8 @@
+package(default_visibility = ["//visibility:private"])
+
+# Export the tests.source so it can be used by Bazel tests elsewhere in the repo.
+sh_library(
+    name = "tests_sh_lib",
+    srcs = ["tests.source"],
+    visibility = ["//tools/build_defs:__pkg__"],
+)

tools/build_defs/golden_test.bzl

@@ -0,0 +1,87 @@
+"""Bazel rules for running golden tests."""
+
+def _gen_test_script(ctx):
+    return """\
+#!/bin/bash
+
+set -uo pipefail
+
+# We don't run 'init' or 'deinit' from tests.source, as these
+# just create & remove a TMP dir and Bazel deals with that for us;
+# instead we just need to ensure that the path for the  Bazel
+# managed temp dir is available in TMP_DIR.
+
+TMP_DIR="$TEST_TMPDIR"
+VERBOSE=true
+DISABLE_ERROR_TESTS=
+SUMMARY_ONLY=
+
+source ./test_suite/tests.source
+
+GOLDEN_OUTPUT=$(cat '{golden_path}')
+
+test_eval '{jsonnet_path}' '{input_path}' '{expected_exit_code}' "$GOLDEN_OUTPUT" '{golden_kind}'
+
+if [ $FAILED -eq 0 ] ; then
+    echo "$0: All $EXECUTED test scripts pass."
+    exit 0
+else
+    echo "$0: FAILED: $FAILED / $EXECUTED"
+    exit 1
+fi
+""".format(
+        jsonnet_path = ctx.executable.jsonnet.short_path,
+        input_path = ctx.file.src.short_path,
+        expected_exit_code = 1 if ctx.attr.expect_error else 0,
+        golden_path = ctx.file.golden.short_path,
+        golden_kind = "PLAIN",
+    )
+
+def _jsonnet_json_golden_test_impl(ctx):
+    test_script = ctx.actions.declare_file(ctx.label.name)
+    ctx.actions.write(
+        output = test_script,
+        is_executable = True,
+        content = _gen_test_script(ctx),
+    )
+    return DefaultInfo(
+        executable = test_script,
+        runfiles = ctx.runfiles(
+            transitive_files = ctx.attr._test_sh_lib.files,
+            files = [
+                ctx.executable.jsonnet,
+                ctx.file.src,
+                ctx.file.golden,
+            ] + ctx.files.data,
+        ),
+    )
+
+jsonnet_json_golden_test = rule(
+    implementation = _jsonnet_json_golden_test_impl,
+    test = True,
+    attrs = {
+        "src": attr.label(
+            mandatory = True,
+            allow_single_file = True,
+        ),
+        "data": attr.label_list(allow_files = True),
+        "golden": attr.label(
+            mandatory = True,
+            allow_single_file = True,
+        ),
+        "jsonnet": attr.label(
+            default = "//cmd:jsonnet",
+            executable = True,
+            cfg = "exec",
+        ),
+        "expect_error": attr.bool(
+            doc = "If True, the golden file is the expected stderr output from jsonnet",
+        ),
+        "canonicalize_golden": attr.bool(
+            doc = "If True, the golden file will be reformatted prior to comparing against the jsonnet output",
+        ),
+        "_test_sh_lib": attr.label(
+            default = "//test_suite:tests_sh_lib",
+        ),
+    },
+)