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bring back std/examples/xeval.ts (#3822)
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48
std/examples/tests/xeval_test.ts
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48
std/examples/tests/xeval_test.ts
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import { xeval } from "../xeval.ts";
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import { stringsReader } from "../../io/util.ts";
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import { decode, encode } from "../../strings/mod.ts";
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import { assertEquals, assertStrContains } from "../../testing/asserts.ts";
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import { test } from "../../testing/mod.ts";
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const { execPath, run } = Deno;
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test(async function xevalSuccess(): Promise<void> {
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const chunks: string[] = [];
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await xeval(stringsReader("a\nb\nc"), ($): number => chunks.push($));
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assertEquals(chunks, ["a", "b", "c"]);
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});
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test(async function xevalDelimiter(): Promise<void> {
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const chunks: string[] = [];
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await xeval(stringsReader("!MADMADAMADAM!"), ($): number => chunks.push($), {
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delimiter: "MADAM"
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});
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assertEquals(chunks, ["!MAD", "ADAM!"]);
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});
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// https://github.com/denoland/deno/issues/2861
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const xevalPath = "examples/xeval.ts";
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test(async function xevalCliReplvar(): Promise<void> {
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const p = run({
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args: [execPath(), xevalPath, "--", "--replvar=abc", "console.log(abc)"],
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stdin: "piped",
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stdout: "piped",
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stderr: "null"
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});
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await p.stdin!.write(encode("hello"));
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await p.stdin!.close();
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assertEquals(await p.status(), { code: 0, success: true });
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assertEquals(decode(await p.output()).trimEnd(), "hello");
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});
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test(async function xevalCliSyntaxError(): Promise<void> {
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const p = run({
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args: [execPath(), xevalPath, "--", "("],
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stdin: "null",
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stdout: "piped",
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stderr: "piped"
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});
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assertEquals(await p.status(), { code: 1, success: false });
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assertEquals(decode(await p.output()), "");
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assertStrContains(decode(await p.stderrOutput()), "Uncaught SyntaxError");
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});
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181
std/examples/xeval.ts
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181
std/examples/xeval.ts
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import { parse } from "../flags/mod.ts";
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const { Buffer, EOF, args, exit, stdin, writeAll } = Deno;
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type Reader = Deno.Reader;
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/* eslint-disable-next-line max-len */
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// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.
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const AsyncFunction = Object.getPrototypeOf(async function(): Promise<void> {})
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.constructor;
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/* eslint-disable max-len */
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const HELP_MSG = `xeval
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Eval a script on lines from stdin.
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Read from standard input and eval code on each whitespace-delimited
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string chunks.
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Print all the usernames in /etc/passwd:
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cat /etc/passwd | deno -A https://deno.land/std/examples/xeval.ts -- "a = $.split(':'); if (a) console.log(a[0])"
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A complicated way to print the current git branch:
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git branch | deno -A https://deno.land/std/examples/xeval.ts -- -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
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Demonstrates breaking the input up by space delimiter instead of by lines:
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cat LICENSE | deno -A https://deno.land/std/examples/xeval.ts -- -d " " "if ($ === 'MIT') console.log('MIT licensed')",
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USAGE:
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deno -A https://deno.land/std/examples/xeval.ts [OPTIONS] <code>
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OPTIONS:
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-d, --delim <delim> Set delimiter, defaults to newline
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-I, --replvar <replvar> Set variable name to be used in eval, defaults to $
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ARGS:
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<code>`;
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/* eslint-enable max-len */
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export type XevalFunc = (v: string) => void;
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export interface XevalOptions {
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delimiter?: string;
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}
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const DEFAULT_DELIMITER = "\n";
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// Generate longest proper prefix which is also suffix array.
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function createLPS(pat: Uint8Array): Uint8Array {
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const lps = new Uint8Array(pat.length);
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lps[0] = 0;
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let prefixEnd = 0;
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let i = 1;
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while (i < lps.length) {
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if (pat[i] == pat[prefixEnd]) {
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prefixEnd++;
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lps[i] = prefixEnd;
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i++;
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} else if (prefixEnd === 0) {
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lps[i] = 0;
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i++;
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} else {
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prefixEnd = pat[prefixEnd - 1];
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}
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}
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return lps;
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}
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// Read from reader until EOF and emit string chunks separated
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// by the given delimiter.
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async function* chunks(
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reader: Reader,
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delim: string
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): AsyncIterableIterator<string> {
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const encoder = new TextEncoder();
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const decoder = new TextDecoder();
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// Avoid unicode problems
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const delimArr = encoder.encode(delim);
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const delimLen = delimArr.length;
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const delimLPS = createLPS(delimArr);
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let inputBuffer = new Buffer();
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const inspectArr = new Uint8Array(Math.max(1024, delimLen + 1));
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// Modified KMP
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let inspectIndex = 0;
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let matchIndex = 0;
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while (true) {
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const result = await reader.read(inspectArr);
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if (result === EOF) {
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// Yield last chunk.
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const lastChunk = inputBuffer.toString();
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yield lastChunk;
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return;
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}
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if ((result as number) < 0) {
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// Discard all remaining and silently fail.
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return;
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}
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const sliceRead = inspectArr.subarray(0, result as number);
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await writeAll(inputBuffer, sliceRead);
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let sliceToProcess = inputBuffer.bytes();
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while (inspectIndex < sliceToProcess.length) {
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if (sliceToProcess[inspectIndex] === delimArr[matchIndex]) {
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inspectIndex++;
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matchIndex++;
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if (matchIndex === delimLen) {
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// Full match
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const matchEnd = inspectIndex - delimLen;
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const readyBytes = sliceToProcess.subarray(0, matchEnd);
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// Copy
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const pendingBytes = sliceToProcess.slice(inspectIndex);
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const readyChunk = decoder.decode(readyBytes);
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yield readyChunk;
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// Reset match, different from KMP.
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sliceToProcess = pendingBytes;
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inspectIndex = 0;
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matchIndex = 0;
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}
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} else {
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if (matchIndex === 0) {
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inspectIndex++;
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} else {
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matchIndex = delimLPS[matchIndex - 1];
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}
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}
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}
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// Keep inspectIndex and matchIndex.
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inputBuffer = new Buffer(sliceToProcess);
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}
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}
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export async function xeval(
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reader: Reader,
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xevalFunc: XevalFunc,
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{ delimiter = DEFAULT_DELIMITER }: XevalOptions = {}
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): Promise<void> {
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for await (const chunk of chunks(reader, delimiter)) {
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// Ignore empty chunks.
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if (chunk.length > 0) {
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await xevalFunc(chunk);
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}
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}
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}
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async function main(): Promise<void> {
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const parsedArgs = parse(args.slice(1), {
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boolean: ["help"],
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string: ["delim", "replvar"],
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alias: {
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delim: ["d"],
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replvar: ["I"],
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help: ["h"]
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},
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default: {
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delim: DEFAULT_DELIMITER,
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replvar: "$"
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}
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});
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if (parsedArgs._.length != 1) {
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console.error(HELP_MSG);
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exit(1);
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}
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if (parsedArgs.help) {
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return console.log(HELP_MSG);
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}
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const delimiter = parsedArgs.delim;
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const replVar = parsedArgs.replvar;
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const code = parsedArgs._[0];
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// new AsyncFunction()'s error message for this particular case isn't great.
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if (!replVar.match(/^[_$A-z][_$A-z0-9]*$/)) {
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console.error(`Bad replvar identifier: "${replVar}"`);
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exit(1);
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}
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const xEvalFunc = new AsyncFunction(replVar, code);
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await xeval(stdin, xEvalFunc, { delimiter });
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}
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if (import.meta.main) {
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main();
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}
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