bluebird-codemod

This repository contains a collection of codemod scripts for use with JSCodeshift that help upgrade usage of bluebird APIs.

The excellent sinon-codemod repository was used as inspiration and served as a template for this repository.

Setup & Run

• npm install -g jscodeshift
• git clone https://github.com/sgilroy/bluebird-codemod.git or download a zip file from https://github.com/sgilroy/bluebird-codemod/archive/master.zip
• Run npm install in the bluebird-codemod directory
  • Alternatively, run yarn to install in the bluebird-codemod directory for a reliable dependency resolution
• jscodeshift -t <codemod-script> <path>
• Use the -d option for a dry-run and use -p to print the output for comparison

New in bluebird 3.0

See the bluebird docs for the full list of changes.

Promisification API changes

The calling convention for Promise.promisify() has changed.

Both promisification (Promise.promisify and Promise.promisifyAll) methods and Promise.fromCallback now by default ignore multiple arguments passed to the callback adapter and instead only the first argument is used to resolve the promise. The behavior in 2.x is to construct an array of the arguments and resolve the promise with it when more than one argument is passed to the callback adapter. The problems with this approach and reasons for the change are discussed in #307.

Promise.promisify's second argument is now an options object, so any code using the second argument needs to change:

// 2.x
Promise.promisify(fn, ctx);
// 3.0
Promise.promisify(fn, {context: ctx});

This calling convention change was introduced in order to support a new option when promisifying, multiArgs.

Setting multiArgs to true means the resulting promise will always fulfill with an array of the callback's success value(s). This is needed because promises only support a single success value while some callback API's have multiple success value. The default is to ignore all but the first success value of a callback function.

.spread's second argument has been removed

Previously, .spread supported a rejected handler as a second argument, like .then. This support for a second argument has been removed and now a separate .catch call should be used instead.

Included Scripts

call-promisify-with-options

Converts the second argument of calls to Promise.promisify(fn, ctx) into Promise.promisify(fn, {context: ctx}).

If the expression has a .spread call chained onto it, the script will infer that multiArgs should be used so that the multiple arguments (not just the first) from the callback can be accessed. Note that this may result in some false-positives where the multiArgs option will need to be manually removed after the script is run. Also, some cases where multiArgs is needed will not be detected automatically and the option will need to be added manually in order to restore the behavior from the pre-3.x version of bluebird. See the unit tests for examples.

jscodeshift -t bluebird-codemod/call-promisify-with-options.js <path>

spread-catch-second-argument

Converts calls to .spread that use a second argument to a combination of .spread (for the fulfilled handler) and .catch (for the rejected handler). That is, calls of promise.spread(fulfilledHandler, rejectedHandler) are converted to promise.spread(fulfilledHandler).catch(rejectedHandler).

jscodeshift -t bluebird-codemod/spread-catch-second-argument.js <path>