traceloc

Trace the current location in a program

Allows access to the file, func, line and col while executing

Prerequisites

• node
• yarn

Usage

Note: typescript types, traceloc.d.ts are integral so there are no @types/traceloc

yarn add traceloc

API

A very simple API there two routines, here(), setProjectRoot() and an interface, ITraceLoc exported:

/**
 * The TraceLoc interface it provides the location
 * infomration and a toString function.
 */
export interface ITraceLoc {
    readonly func: string;
    readonly file: string;
    readonly line: number;
    readonly col: number;
    toString(): string;
}
/**
 * The user may change to expected root of the project
 * and filepaths returned file ITraceLoc.file will be
 * relative to the root parameter. The default if not set
 * (i.e. "", undefined or null) is ".", the current
 * working directory.
 *
 * @param root is the full path to the directory containing the project
 * @param returns previous value
 */
export declare function setProjectRoot(root: string | undefined | null): string | undefined | null;
/**
 * Return the ITraceLoc oject.
 *
 * @param callDepth is the stackframe index which to retrieve
 *        the location information. Defaults to 0. A non-zero
 *        value can be used to provide the location for the
 *        n'th entry on stackframe. This is useful if custom
 *        here() is created that calls this here(). See
 *        example/t3.ts.
 * @return ITraceLoc
 */
export declare function here(callDepth?: number): ITraceLoc;

Examples:

Before running these examples run yarn install-self.

The simplest possible example is something like:

$ cat -n examples/t1.ts
     1	import { here } from "traceloc";
     2	console.log(`Hello from ${here()}`);
$ tsc --sourceMap examples/t1.ts
$ node examples/t1.js
Hello from Object.<anonymous> examples/t1.ts:2:27

Here using here() in a subroutine and the location variables:

$ cat -n examples/t2.ts
     1	import { here } from "traceloc";
     2	
     3	function sub() {
     4	    let loc = here();
     5	    console.log(`sub: func=${loc.func} file=${loc.file} line=${loc.line} col=${loc.col}`);
     6	}
     7	
     8	sub();
$ tsc --sourceMap examples/t2.ts
$ node examples/t2.js
sub: func=sub file=examples/t2.ts line=4 col=15

The final example we create our own log subroutine calling here(1). The callDepth parameter, 1, requests here to get the location of the caller of log(sring):

$ cat -n examples/t3.ts
     1	import { here } from "traceloc";
     2	
     3	let LOGGING = true;
     4	
     5	function log(prompt: string) {
     6	    if (LOGGING) {
     7	        let loc = here(1); // Get the location of the caller
     8	        console.log(`${prompt}: ${loc.func}:${loc.line}`);
     9	    }
    10	}
    11	
    12	function sub() {
    13	    log("enter");
    14	    LOGGING = false;
    15	    log("no output expected");
    16	    LOGGING = true;
    17	    console.log("Ready to exit");
    18	    log("exit");
    19	}
    20	
    21	sub();
$ tsc --sourceMap examples/t3.ts
$ node examples/t3.js
enter: sub:13
Ready to exit
exit: sub:18

To Hack on this code

Clone the repo

git clone https://github.com/winksaville/traceloc

Install dependencies

yarn install

Test

The test target also builds.

yarn test

You can also build separately.

yarn build

There is also Coverage which target builds, tests and output coverage data using nyc

yarn coverage

Benchmark

On my laptop here() runs at about 7,000 ops/sec this is quite slow, for comparison a routine that increaments its parameter runs at 80,000,000 ops/sec.

To run the benchmark:

yarn benchmark

To run and append the results:

yarn benchmark:save