coderaiserESTrace 
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