Jsonnet Rules

Rules

• jsonnet_library
• jsonnet_to_json
• jsonnet_to_json_test

Overview

These are build rules for working with Jsonnet files with Bazel.

Setup

To use the Jsonnet rules, add the following to your WORKSPACE file to add the external repositories for Jsonnet:

http_archive(
    name = "io_bazel_rules_jsonnet",
    url = "https://github.com/bazelbuild/rules_jsonnet/archive/0.0.2.tar.gz",
    sha256 = "5f788c7719a02ed2483641365f194e9e5340fbe54963d6d6caa09f91454d38b8",
    strip_prefix = "rules_jsonnet-0.0.2",
)
load("@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl", "jsonnet_repositories")

jsonnet_repositories()

jsonnet_library

jsonnet_library(name, srcs, deps, imports)

Attributes
name	Name, required A unique name for this rule.
srcs	List of Labels, required List of .jsonnet files that comprises this Jsonnet library.
deps	List of labels, optional List of targets that are required by the srcs Jsonnet files.
imports	List of strings, optional List of import -J flags to be passed to the jsonnet compiler.

Example

Suppose you have the following directory structure:

[workspace]/
    WORKSPACE
    configs/
        BUILD
        backend.jsonnet
        frontend.jsonnet

You can use the jsonnet_library rule to build a collection of .jsonnet files that can be imported by other .jsonnet files as dependencies:

configs/BUILD:

load("@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl", "jsonnet_library")

jsonnet_library(
    name = "configs",
    srcs = [
        "backend.jsonnet",
        "frontend.jsonnet",
    ],
)

jsonnet_to_json

jsonnet_to_json(name, src, deps, outs, multiple_outputs, imports, vars, code_vars)

Attributes
name	Name, required A unique name for this rule. This name will be used as the name of the JSON file generated by this rule.
src	Label, required The .jsonnet file to convert to JSON.
deps	List of labels, optional List of targets that are required by the src Jsonnet file.
outs	List of Filenames, required Names of the output .json files to be generated by this rule. If you are generating only a single JSON file and are not using jsonnet multiple output files, then this attribute should only contain the file name of the JSON file you are generating. If you are generating multiple JSON files using jsonnet multiple file output (jsonnet -m), then list the file names of all the JSON files to be generated. The file names specified here must match the file names specified in your src Jsonnet file. For the case where multiple file output is used but only for generating one output file, set the multiple_outputs attribute to 1 to explicitly enable the -m flag for multiple file output.
multiple_outputs	bool, optional, default 0 Set to 1 to explicitly enable multiple file output via the jsonnet -m flag. This is used for the case where multiple file output is used but only for generating a single output file. For example: local foo = import "foo.jsonnet"; { "foo.json": foo, }
imports	List of strings, optional List of import -J flags to be passed to the jsonnet compiler.
vars	String dict, optional Map of variables to pass to jsonnet via --var key=value.
code_vars	String dict, optional Map of code variables to pass to jsonnet via --code-var key=value.

Example

Suppose you have the following directory structure:

[workspace]/
    WORKSPACE
    workflows/
        BUILD
        workflow.libsonnet
        wordcount.jsonnet
        intersection.jsonnet

Say that workflow.libsonnet is a base configuration library for a workflow scheduling system and wordcount.jsonnet and intersection.jsonnet both import workflow.libsonnet to define workflows for performing a wordcount and intersection of two files, respectively.

First, create a jsonnet_library target with workflow.libsonnet:

workflows/BUILD:

load("@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl", "jsonnet_library")

jsonnet_library(
    name = "workflow",
    srcs = ["workflow.libsonnet"],
)

To compile wordcount.jsonnet and intersection.jsonnet to JSON, define two jsonnet_to_json targets:

jsonnet_to_json(
    name = "wordcount",
    src = "wordcount.jsonnet",
    outs = ["wordcount.json"],
    deps = [":workflow"],
)

jsonnet_to_json(
    name = "intersection",
    src = "intersection.jsonnet",
    outs = ["intersection.json"],
    deps = [":workflow"],
)

Example: Multiple output files

To use Jsonnet's multiple output files, suppose you add a file shell-workflows.jsonnet that imports wordcount.jsonnet and intersection.jsonnet:

workflows/shell-workflows.jsonnet:

local wordcount = import "workflows/wordcount.jsonnet";
local intersection = import "workflows/intersection.jsonnet";

{
  "wordcount-workflow.json": wordcount,
  "intersection-workflow.json": intersection,
}

To compile shell-workflows.jsonnet into the two JSON files, wordcount-workflow.json and intersection-workflow.json, first create a jsonnet_library target containing the two files that shell-workflows.jsonnet depends on:

jsonnet_library(
    name = "shell-workflows-lib",
    srcs = [
        "wordcount.jsonnet",
        "intersection.jsonnet",
    ],
    deps = [":workflow"],
)

Then, create a jsonnet_to_json target and set outs to the list of output files to indicate that multiple output JSON files are generated:

jsonnet_to_json(
    name = "shell-workflows",
    src = "shell-workflows.jsonnet",
    deps = [":shell-workflows-lib"],
    outs = [
        "wordcount-workflow.json",
        "intersection-workflow.json",
    ],
)

jsonnet_to_json_test

jsonnet_to_json_test(name, src, deps, imports, golden, error=0, regex=False)

Attributes
name	Name, required A unique name for this rule. This name will be used as the name of the JSON file generated by this rule.
src	Label, required The .jsonnet file to convert to JSON.
deps	List of labels, optional List of targets that are required by the src Jsonnet file.
imports	List of strings, optional List of import -J flags to be passed to the jsonnet compiler.
vars	String dict, optional Map of variables to pass to jsonnet via --var key=value.
code_vars	String dict, optional Map of code variables to pass to jsonnet via --code-var key=value.
golden	Label, optional The expected (combined stdout and stderr) output to compare to the output of running jsonnet on src.
error	Integer, optional, default is 0 The expected error code from running jsonnet on src.
regex	bool, optional, default is False Set to 1 if golden contains a regex used to match the output of running jsonnet on src.

Example

Suppose you have the following directory structure:

[workspace]/
    WORKSPACE
    config/
        BUILD
        base_config.libsonnet
        test_config.jsonnet
        test_config.json

Suppose that base_config.libsonnet is a library Jsonnet file, containing the base configuration for a service. Suppose that test_config.jsonnet is a test configuration file that is used to test base_config.jsonnet, and test_config.json is the expected JSON output from compiling test_config.jsonnet.

The jsonnet_to_json_test rule can be used to verify that compiling a Jsonnet file produces the expected JSON output. Simply define a jsonnet_to_json_test target and provide the input test Jsonnet file and the golden file containing the expected JSON output:

config/BUILD:

load(
    "@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl",
    "jsonnet_library",
    "jsonnet_to_json_test",
)

jsonnet_library(
    name = "base_config",
    srcs = ["base_config.libsonnet"],
)

jsonnet_to_json_test(
    name = "test_config_test",
    src = "test_config",
    deps = [":base_config"],
    golden = "test_config.json",
)

To run the test: bazel test //config:test_config_test

Example: Negative tests

Suppose you have the following directory structure:

[workspace]/
    WORKSPACE
    config/
        BUILD
        base_config.libsonnet
        invalid_config.jsonnet
        invalid_config.output

Suppose that invalid_config.jsonnet is a Jsonnet file used to verify that an invalid config triggers an assertion in base_config.jsonnet, and invalid_config.output is the expected error output.

The jsonnet_to_json_test rule can be used to verify that compiling a Jsonnet file results in an expected error code and error output. Simply define a jsonnet_to_json_test target and provide the input test Jsonnet file, the expected error code in the error attribute, and the golden file containing the expected error output:

config/BUILD:

load(
    "@io_bazel_rules_jsonnet//jsonnet:jsonnet.bzl",
    "jsonnet_library",
    "jsonnet_to_json_test",
)

jsonnet_library(
    name = "base_config",
    srcs = ["base_config.libsonnet"],
)

jsonnet_to_json_test(
    name = "invalid_config_test",
    src = "invalid_config",
    deps = [":base_config"],
    golden = "invalid_config.output",
    error = 1,
)

To run the test: bazel test //config:invalid_config_test