resolveParentPathBy

Resolve a path according to a predicate function by walking parent directories.

Usage

var resolveParentPathBy = require( '@stdlib/fs/resolve-parent-path-by' );

resolveParentPathBy( path[, options], predicate, clbk )

Asynchronously resolves a path according to a predicate function by walking parent directories.

resolveParentPathBy( 'package.json', predicate, onPath );

function predicate( path, next ) {
    var bool = ( /\/test\//.test( path ) === false );
    next( null, bool );
}

function onPath( error, path ) {
    if ( error ) {
        throw error;
    }
    console.log( path );
    // e.g., => '...'
}

The function accepts the following options:

  • dir: base directory from which to begin walking. May be either an absolute path or a path relative to the current working directory.

By default, the function begins walking from the current working directory. To specify an alternative directory, set the dir option.

var opts = {
    'dir': __dirname
};
resolveParentPathBy( 'package.json', opts, predicate, onPath );

function predicate( path, next ) {
    var bool = ( /\/test\//.test( path ) === false );
    next( null, bool );
}

function onPath( error, path ) {
    if ( error ) {
        throw error;
    }
    console.log( path );
    // e.g., => '...'
}

When invoked, the predicate function is provided two arguments:

  • path: a resolved path.
  • next: a callback which should be called once the predicate function has finished processing a resolved path.

If a predicate function calls the next callback with a truthy second argument, the function stops processing any additional paths and returns the resolved path as the test result.

If unable to resolve a path, the function returns null as the path result.

resolveParentPathBy.sync( path[, options], predicate )

Synchronously resolves a path according to a predicate function by walking parent directories.

function predicate( path ) {
    return ( /\/test\//.test( path ) === false );
}

var path = resolveParentPathBy.sync( 'package.json', predicate );
// e.g., returns '...'

The function accepts the same options as resolveParentPathBy().

When invoked, the predicate function is provided one argument:

  • path: a resolved path.

The function immediately returns upon encountering a truthy predicate function return value.

If unable to resolve a path, the function returns null as the path result.

Notes

  • If a provided predicate function calls the next callback with a truthy error argument, the function suspends execution and immediately calls the done callback for subsequent error handling.
  • For resolveParentPathBy, execution is not guaranteed to be asynchronous. To guarantee asynchrony, wrap the done callback in a function which either executes at the end of the current stack (e.g., nextTick) or during a subsequent turn of the event loop (e.g., setImmediate, setTimeout).
  • This implementation is not similar in functionality to core path.resolve. The latter performs string manipulation to generate a full path. This implementation walks parent directories to perform a search, thereby touching the file system. Accordingly, this implementation resolves a real absolute file path and is intended for use when a target's location in a parent directory is unknown relative to a child directory; e.g., when wanting to find a package root from deep within a package directory.

Examples

var resolveParentPathBy = require( '@stdlib/fs/resolve-parent-path-by' );

var opts = {
    'dir': __dirname
};

/* Sync */

function predicateSync( path ) {
    var pkg = require( path );
    if ( pkg.name !== '@stdlib/stdlib' ) {
        return false;
    }
    return true;
}

var out = resolveParentPathBy.sync( 'package.json', opts, predicateSync );
console.log( out );
// e.g., => '...'

out = resolveParentPathBy.sync( 'non_existent_basename/package.json', predicateSync );
console.log( out );
// => null

/* Async */

function predicateAsync( path, next ) {
    setTimeout( onTimeout, 0 );

    function onTimeout() {
        var pkg = require( path );
        if ( pkg.name !== '@stdlib/stdlib' ) {
            return next( null, false );
        }
        next( null, true );
    }
}

function onPath( error, path ) {
    if ( error ) {
        throw error;
    }
    console.log( path );
}

resolveParentPathBy( 'package.json', opts, predicateAsync, onPath );
resolveParentPathBy( './../non_existent_path/package.json', predicateAsync, onPath );

See Also

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