module-async-mapper
Discover and specify module methods' continuation schemes (callbacks vs promises vs generator functions, etc)
mapper.map(module[, hints, options])
Traverses the module and returns a JSONPath style map of the given module's methods, along with a heuristic best guess at their continuation scheme, accepting hints to inform guesses.
var mapper = ;var fs = ;var map = mapper; // {// '$.readFile': 'standard',// '$.readFileSync': 'sync',// '$.writeFile': 'standard',// '$.writeFileSync': 'sync',// '$.exists': 'simple',// '$.existsSync': 'sync',// ...// }
Hints are in the form of an object with JSONPath keys pointing to continuation scheme identifiers, optionally preceded by a +
to force that option to take effect.
And another example: The mkdirp
module exports a function that accepts a standard node callback, but that happens to be difficult to ascertain programmatically so we provide a hint.
var mapper = ;var mkdirp = ;var map = mapper; // {// '$': 'standard',// '$.sync': 'sync'// }
If module
is a string, it will be resolved as require
would do, and any hints in .asyncmap.json
in the module's source root will be applied with hints
merged on top, as well as any local hints from this package.
Takes the following options:
traverseAll
- Traverse the whole object rather than just the parts that match keys in hints; defaults totrue
loadModuleHints
- Load any hints from.asyncmap
files in module source root; defaults totrue
loadLocalHints
- Load any hints fromhints
in this here module; defaults totrue
mapper.scheme(fn)
Given a function returns a continuation scheme identifier based on a heuristic best guess. For example, detect a plain old synchronous function:
var scheme = mapperscheme { return a + b };// "sync"
Or detect a function that accepts a standard callback:
var scheme = mapperscheme { return };// "standard"
Continuation Schemes
JavaScript has a few options/conventions for continuing execution with the result of some asynchronous action.
Standard Node Callback
standard
The most common and scheme is the standard
node callback -- a function that accepts an error as the first parameter and a return value as the second.
fs;
Simple Callback
simple
An optimistic callback function, accepting just the return value as the first paramater, with no intrinsic mechanism for reporting error.
fs;
Promise
promise
A promise is an instance of a Promise from ES6 promises / bluebird / etc.
File ;
Generator Function
generator
A generator function may perform asynchronous work and assign results of that work via yield
ing within its body. Requires a framework like suspend as an intermediary.
;
Synchronous Return
sync
A regular old function that directly returns the result of its work, potentially blocking the event loop for any I/O operations.
var contents = fs;console;
License
MIT