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estrace

v5.1.1

Published

trace functions of EcmaScript modules

Downloads

1,515

Readme

ESTrace License NPM version Build Status Coverage Status

Trace functions in Node.js EcmaScript Modules. For CommonJS use njsTrace.

Install

npm i estrace

Run

Loaders used to get things done, run with --loader flag:

NODE_OPTIONS="'--loader estrace --no-warnings'" node lint.js

Perf

When you want to see report of the most hot function calls count use:

NODE_OPTIONS="'--loader estrace/perf --no-warnings'" node example/perf.js

Example

Let's suppose you want to trace lint.js:

const checkFile = (a) => a;
lint();

function lint(runners) {
    const files = getFiles(runners);
    const checkedFiles = checkFiles(files);
    
    return checkedFiles;
}

function getFiles(runners) {
    const files = [];
    
    for (const run of runners) {
        files.push(...run());
    }
    
    return files;
}

function lintFiles(files) {
    const linted = [];
    
    for (const file of files) {
        linted.push(checkFile(file));
    }
    
    return linted;
}

You will see something like this

coderaiser@cloudcmd:~/estrace$ node --loader estrace example/lint.js
..💣 lint([]) 16.05mb file:///Users/coderaiser/estrace/example/lint.js:5
....💣 getFiles([]) 16.05mb file:///Users/coderaiser/estrace/example/lint.js:12
....💥 getFiles 16.06mb file:///Users/coderaiser/estrace/example/lint.js:12
....💣 lintFiles([]) 16.06mb file:///Users/coderaiser/estrace/example/lint.js:22
....💥 lintFiles 16.06mb file:///Users/coderaiser/estrace/example/lint.js:22
..💥 lint 16.06mb file:///Users/coderaiser/estrace/example/lint.js:5

How ESTrace works?

Let's suppost you have a function: const fn = (a) => a. EStrace will replace it with:

const fn = (a) => {
    try {
        var __estrace_context = __estrace.enter('<anonymous:2>', 'file://hello.js:2', arguments);
        return a;
    } finally {
        __estrace.exit('<anonymous:2>', 'file://hello.js:2', __estrace_context);
    }
};

And you cat get more information about the way your code works.

Ignore function

When you need to ignore a function, just add __estrace.ignore() before function:

export /* __estrace.ignore() */
function enter() {}

And ESTrace won't touch it.

Using as plugin

First of all ESTrace is plugin for 🐊Putout and it can be used independely:

import putout from 'putout';
import {estracePlugin} from 'estrace/plugin';

const source = `
    const fn = (a) => a;
`;

const {code} = putout(source, {
    plugins: [estracePlugin],
});

console.log(code);

Passing file url

If you need to pass url, you can with help of rules :

const {code} = putout(source, {
    rules: {
        'estrace/trace': ['on', {
            url: 'file://hello.js',
        }],
    },
    plugins: [estracePlugin],
});

Exclude functions

When you need to exclude some kinds of functions, you can use universal cross-plugin way:

const {code} = putout(source, {
    rules: {
        'estrace/trace': ['on', {
            url: 'file://hello.js',
            exclude: [
                'ArrowFunctionExpression',
            ],
        }],
    },
    plugins: [estracePlugin],
});

Overriding plugin name

If for some reason you need to override the name of a plugin, you can use default import and name it in a way you like.

import putout from 'putout';
import funnyTracer from 'estrace/plugin';

const source = `
    const fn = (a) => a;
`;

const {code} = putout(source, {
    rules: {
        'funnyTracer/trace': ['on', {
            url: 'file://hello.js',
        }],
    },
    plugins: [
        ['funnyTracer', funnyTracer],
    ],
});

console.log(code);

Supported function types:

FunctionDeclaration (named):

function hello() {
    return 'world';
}

FunctionExpression (anonymous):

hello(function(word) {
    return `hello ${word}`;
});

ArrowFunctionExpression (arrow):

hello((word) => {
    return `hello ${word}`;
});

ClassMethod (method):

class Hello {
    hello(word) {
        return `hello ${word}`;
    }
}

License

MIT