Create compatIO utility functions (#1637)
Currently similar code to read/write Compatible JSON files is copy pasted across the code. This takes some common practices and provides a generic utility for it. Correct Flow type usage can't be detected if the JSON type is opaque though. GraphJSON is an example of this, so removed the opaque for a smoke test.
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Robin van Boven
GitHub
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// @flow
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import fs from "fs-extra";
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import stringify from "json-stable-stringify";
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import {type Compatible} from "../util/compat";
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/**
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* Utility functions, which allow us to read/write a Compatible of any
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* type to a JSON file. They should automatically detect the Flow types
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* and produce errors when misused.
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*
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* Note, the Compatible<T> type used cannot be opaque.
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*/
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/**
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* Creates a Compatible JSON file writer.
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* The writer's Flow type for `data` will automatically match the provided
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* `toJSON`'s argument type.
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* Optionally takes a `typeName` to improve error messages.
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*/
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export function compatWriter<T, J>(
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toJSON: (T) => Compatible<J>,
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typeName?: string
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): (path: string, data: T) => Promise<void> {
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return async (path: string, data: T): Promise<void> => {
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try {
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await fs.writeFile(path, stringify(toJSON(data)));
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} catch (e) {
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throw new Error(
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`Could not write ${typeName ? typeName + " " : ""}data:\n${e}`
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);
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}
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};
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}
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/**
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* Creates a Compatible JSON file reader.
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* The reader's Flow type for the return value will automatically match the
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* provided `fromJSON`'s return type.
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* Optionally takes a `typeName` to improve error messages.
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*/
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export function compatReader<T>(
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fromJSON: (Compatible<any>) => T,
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typeName?: string
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): (path: string) => Promise<T> {
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return async (path: string): Promise<T> => {
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if (!(await fs.exists(path))) {
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throw new Error(
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`Could not find ${typeName ? typeName + " " : ""}file at: ${path}`
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);
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}
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try {
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return fromJSON(JSON.parse(await fs.readFile(path)));
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} catch (e) {
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throw new Error(
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`Provided ${typeName ? typeName + " " : ""}file is invalid:\n${e}`
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);
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}
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};
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}
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@ -0,0 +1,244 @@
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// @flow
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import tmp from "tmp";
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import path from "path";
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import fs from "fs-extra";
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import {type Compatible, toCompat, fromCompat} from "../util/compat";
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import {createProject, projectToJSON, projectFromJSON} from "../core/project";
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import {Graph} from "../core/graph";
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import * as WeightedGraph from "../core/weightedGraph";
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import {node as graphNode} from "../core/graphTestUtil";
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import {compatWriter, compatReader} from "./compatIO";
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type MockDataType = {+[string]: string};
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const mockCompatInfo = {type: "mock", version: "1"};
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function mockToJSON(x: MockDataType): Compatible<MockDataType> {
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return toCompat(mockCompatInfo, x);
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}
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function mockFromJSON(x: Compatible<any>): MockDataType {
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return fromCompat(mockCompatInfo, x);
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}
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describe("src/backend/compatIO", () => {
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describe("compatWriter", () => {
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it("should work with example type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const data: MockDataType = {foo: "bar"};
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// When
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const writer = compatWriter(mockToJSON);
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await writer(filePath, data);
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// Then
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const actualData = await fs.readFile(filePath, "utf8");
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expect(actualData).toEqual(
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`[{"type":"mock","version":"1"},{"foo":"bar"}]`
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);
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});
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it("should handle write errors", async () => {
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// Given
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const filePath = tmp.dirSync().name;
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const data: MockDataType = {foo: "bar"};
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// When
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const writer = compatWriter(mockToJSON);
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const p = writer(filePath, data);
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// Then
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await expect(p).rejects.toThrow("Could not write data:\nError: EISDIR");
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});
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it("should accept a typeName to improve errors", async () => {
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// Given
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const filePath = tmp.dirSync().name;
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const data: MockDataType = {foo: "bar"};
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const name = "TestName";
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// When
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const writer = compatWriter(mockToJSON, name);
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const p = writer(filePath, data);
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// Then
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await expect(p).rejects.toThrow(
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`Could not write ${name} data:\nError: EISDIR`
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);
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});
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it("should use stable json serialization", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const data: MockDataType = {bbb: "second", aaa: "first"};
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// When
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const writer = compatWriter(mockToJSON);
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await writer(filePath, data);
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// Then
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const actualData = (await fs.readFile(filePath)).toString("utf-8");
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expect(actualData).toEqual(
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`[{"type":"mock","version":"1"},{"aaa":"first","bbb":"second"}]`
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);
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});
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});
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describe("compatReader", () => {
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it("should work with example type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const fileContents = `[{"type":"mock","version":"1"},{"foo":"bar"}]`;
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await fs.writeFile(filePath, fileContents);
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// When
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const reader = compatReader(mockFromJSON);
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const data = await reader(filePath);
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// Then
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expect(data).toEqual({foo: "bar"});
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});
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it("should check the file exists", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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// When
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const reader = compatReader(mockFromJSON);
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const p = reader(filePath);
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// Then
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await expect(p).rejects.toThrow("Could not find file at:");
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});
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it("should check for invalid file content", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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await fs.writeFile(filePath, "-not valid JSON-");
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// When
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const reader = compatReader(mockFromJSON);
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const p = reader(filePath);
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// Then
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await expect(p).rejects.toThrow(
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"Provided file is invalid:\nSyntaxError: Unexpected token"
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);
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});
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it("should check for invalid compat type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const fileContents = `[{"type":"wrong-type","version":"1"},{"foo":"bar"}]`;
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await fs.writeFile(filePath, fileContents);
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// When
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const reader = compatReader(mockFromJSON);
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const p = reader(filePath);
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// Then
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await expect(p).rejects.toThrow(
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"Provided file is invalid:\nError: Expected type to be mock but got wrong-type"
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);
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});
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it("should check for invalid compat version", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const fileContents = `[{"type":"mock","version":"2"},{"foo":"bar"}]`;
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await fs.writeFile(filePath, fileContents);
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// When
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const reader = compatReader(mockFromJSON);
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const p = reader(filePath);
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// Then
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await expect(p).rejects.toThrow(
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"Provided file is invalid:\nError: mock: tried to load unsupported version 2"
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);
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});
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it("should accept a typeName to improve errors", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const name = "TestName";
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// When
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const reader = compatReader(mockFromJSON, name);
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const p = reader(filePath);
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// Then
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await expect(p).rejects.toThrow(`Could not find ${name} file at:`);
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});
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});
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describe("compatReader + compatWriter", () => {
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it("should work as a round-trip", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "mockData.json");
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const data: MockDataType = {foo: "bar"};
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// When
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const writer = compatWriter(mockToJSON);
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const reader = compatReader(mockFromJSON);
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await writer(filePath, data);
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const actualData = await reader(filePath);
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// Then
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expect(actualData).toEqual(data);
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});
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// Note: this is a smoke test and can be safely removed if needed.
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it("should work with Project Compatible type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "project.json");
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const project = createProject({id: "example-project"});
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// When
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const writer = compatWriter(projectToJSON);
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const reader = compatReader(projectFromJSON);
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await writer(filePath, project);
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const actual = await reader(filePath);
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// Then
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expect(actual).toEqual(project);
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});
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// Note: this is a smoke test and can be safely removed if needed.
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it("should work with Graph Compatible type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "graph.json");
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const graph = new Graph();
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graph.addNode(graphNode("example-node"));
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// When
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const writer = compatWriter((g: Graph) => g.toJSON());
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const reader = compatReader(Graph.fromJSON);
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await writer(filePath, graph);
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const actual = await reader(filePath);
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// Then
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expect(actual.equals(graph)).toBe(true);
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});
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// Note: this is a smoke test and can be safely removed if needed.
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it("should work with WeightedGraph Compatible type", async () => {
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// Given
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const filePath = path.join(tmp.dirSync().name, "weightedGraph.json");
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const wg = WeightedGraph.empty();
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wg.graph.addNode(graphNode("example-node"));
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// When
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const writer = compatWriter(WeightedGraph.toJSON);
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const reader = compatReader(WeightedGraph.fromJSON);
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await writer(filePath, wg);
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const actual = await reader(filePath);
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// Then
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expect(actual.graph.equals(wg.graph)).toBe(true);
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expect(actual.weights).toEqual(wg.weights);
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});
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});
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});
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@ -191,7 +191,7 @@ type IndexedEdgeJSON = {|
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+timestampMs: number,
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|};
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export opaque type GraphJSON = Compatible<{|
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export type GraphJSON = Compatible<{|
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// A node address can be present because it corresponds to a node, or because
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// it is referenced by a dangling edge.
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+sortedNodeAddresses: AddressJSON[],
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