@seflage/generator_cli

Install

npm install @selfage/generator_cli

Overview

Written in TypeScript and compiled to ES6 with inline source map & source. See @selfage/tsconfig for full compiler options. Provides a CLI to generate TypeScript code based on definitions written in JSON. See commander if you are not sure about CLI syntax.

It can generate messages, observables, Google Datastore client, Google Spanner SQL interfaces, web service client, and service handler. Generated code would require corresponding runtime lib to run, which can be installed separately.

CLI

$ geneage -h
Usage: geneage [options] <definitionFile>

Generate various TypeScript codes from the definition file written in JSON.

Options:
  -V, --version                 output the version number
  -i, --index-file <indexFile>  The index yaml file for Google Cloud Datastore composite index. Its file ext can be neglected and is always fixed as .yaml. Requried only if
                                your definition file includes a datastore definition. You can also add '"datastoreIndex": "./your/index_file"' to your package.json file to
                                save typings.
  --dry-run                     Print the generated content instead of writing it to the destination file.
  -h, --help                    display help for command

Examples

All code generation examples can be found under test_data/generator/ directory.

Another example to use index file when generating datastore clients is $ geneage test_data/generator/datastore/task -i test_data/generator/datastore/index, where test_data/generator/datastore/task.json is the input, and test_data/generator/datastore/task.ts and test_data/generator/datastore/task_model.ts are the output, while test_data/generator/datastore/index is both the input and output.

Message

The term "message" stands for data class, inspired from Google's Protocol Buffers, i.e., in JavaScript/TypeScript case, an object without any functions defined on it, which is what can be communicated between different threads, processes, or distributed servers.

TypeScript uses interfaces to describe objects at compiling time, checking for invalid references to object fields/properties. However, in cases such as casting JSON.parse(...) to a type-safe object, JSON.parse(...) as MyData doesn't really validate fields for you and thus you don't get a real type-safe object.

The runtime lib @selfage/message can parse, copy and merge messages, while validate each field. It requires generated MessageDescriptors.

Examples can be found under test_data/generator/message. E.g. $ geneage test_data/generator/message/user_info, where test_data/generator/message/user_info.json is the input and test_data/generator/message/user_info.ts is the output.

JSON definition files are like TypeScript interface but a little bit verbose. The supported types are string, boolean and number, enums, and messages.

Observable

An observable object exposes events/callbacks to observe every state change.

The runtime lib @selfage/observable can parse, copy and merge observable. It requires generated ObservableDescriptors.

Examples can be found under test_data/generator/observable. E.g. $ geneage test_data/generator/observable/item, where test_data/generator/observable/item.json is the input and test_data/generator/observable/item.ts is the output.

Note that there are two types of arrays here, normal and observable, which should be self-explanatory. The supported types are string, boolean and number, enums, messages, and observables.

Datastore client

The runtime lib selfage/datastore_client provides type-safe Google Cloud Datastore APIs as a thin layer on top of @google-cloud/datastore, though requires generated DatastoreModelDescriptors and QueryBuilders.

Examples can be found under test_data/generator/datastore. E.g., $ geneage test_data/generator/datastore/task -i test_data/generator/datastore/index, where test_data/generator/datastore/task.json is the input, and test_data/generator/datastore/task.ts and test_data/generator/datastore/task_model.ts are the output, while test_data/generator/datastore/index is both the input and output.

A few notes about index.yaml.

1. It contains composite indexes and is required to be uploaded to Google Datastore manually. It's not used by the runtime lib selfage/datastore_client directly.
2. It's generated based on the exact order of filters and orderings for each of queries. So the order matters a lot! It's recommended to read through Datastore's document carefully about queries and indexes, especially note how the order of fields/properties in a composite index affects the kinds of queries supported. Generating indexes this way is to keep it more manageable and predictable. You may still have to handcraft some super advanced indexes.
3. If you already have index.yaml, the above command will update index.yaml to include new indexes and will never delete indexes from index.yaml even if you deleted queries from your JSON definition file. You have to delete unused indexes manually from index.yaml and upload it to Datastore, because those indexes might still be used in the servers.

Spanner SQL

The runtime lib is Google's standard client @google-cloud/spanner. Though you can handcraft SQL queries, this CLI helps you prepare params and parse output with type-safe interfaces.

Examples can be found under test_data/generator/spanner. E.g., $ geneage test_data/generator/spanner/query, where test_data/generator/spanner/query.json is the input and test_data/generator/spanner/query.ts is the output.

The SQL syntax is exactly the same as documented by Spanner. You only need to spell out the types of params and output columns. Unfortunately, it's not capable of validating the SQL syntax or making sure the types you spelled out are matching your database's definition.

The supported types are string, bool, int53, float, timestamp, and bytes. Other types, including struct and array of array, are not supported. They are translated to Spanner and Nodejs types as the following.

1. float maps to float64 in Spanner and number in JS/TS.
2. timestamp maps to timestamp in Spanner and number in milliseconds in JS/TS.
3. string and bool are the same in Spanner and JS/TS.
4. bytes maps to bytes in Spanner and Nodejs Buffer in JS/TS.
5. int53 maps to int64 in Spanner and number in JS/TS. By specifying int53, it means that you can guarantee the number stored won't exceed the max number in JS which is 2^53 - 1. int64 is left out here until bigint is better supported.

Service client & handler

There are two runtime libs, @selfage/web_service_client to be used in web browsers for calling to backend services via HTTP, and @selfage/service_handler to be used in backend servers for implementing HTTP service handlers.

Examples can be found under test_data/generator/service. E.g., $ geneage test_data/generator/service/service, test_data/generator/service/service.json is the input, and test_data/generator/service/service.ts, test_data/generator/service/client.ts, and test_data/generator/service/handler.ts are the output.

response can only be a message. body refers to the HTTP body in a request, and it can be either bytes or another message. Both response and body fields are required.

side and signedUserSession will be encoded to URL params, where keys are specified by their key field, and values are encoded from their type field which can only be another message.

Other usage

The schema of a JSON definition file is an array of definition, where you can find more comprehensive documents and advanced fields.

API access

import { generate } from "@selfage/cli/generate/generator" is the function invoked by the CLI.