Allow concise ArrowFunctionExpression (named-functions-in-promises) #64

sudowork · 2017-05-19T19:42:17Z

In relation to #63, this is the change I'm proposing to support binding context using arrow functions while still maintaining while still maintaining testability.

Here's the example for reference:

export default Component.extend({
  actions: {
    updateUser(user) {
      user.save()
        .then(user => this._reloadUser(user))
        .then(() => this._notifyAboutSuccess())
        .catch(err => this._notifyAboutFailure(err));
        //  As opposed to:
        // .then(this._reloadUser.bind(this))
        // .then(this._notifyAboutSuccess.bind(this))
        // .catch(this._notifyAboutFailure.bind(this));
    },
  },

  // ... Imagine there's a lot of other functions here ...

  _reloadUser(user) {
    return user.reload();
  },
  _notifyAboutSuccess() { /* ... */ },
  _notifyAboutFailure(err) { /* ... */ },
});

Note: This change explicitly allows the concise version of an ArrowFunctionExpression and does not allow arrow functions with explicit () => { /* function bodies */ }. In addition, it checks to ensure that the expression body is a CallExpression to ensure the logic is not happening in the arrow function itself.

Fixes #63

This is to ensure that the promise handler is defined as a method on the parent object and not some other object.

sudowork · 2017-05-19T20:18:44Z

Edit: This is no longer the case as of 4d01fda after some discussion in #63.

Made the allowable case even more stringent by ensuring that the CallExpression is calling a method on the parent:

// GOOD
user.save()
  .then(() => this._reloadUser(user))
  .catch(err => this._notifyAboutFailure(err))

// BAD
user.save()
  .then(() => user.reload())
  .catch(err => this._notifyAboutFailure(err))

While I'm not sure if this is being too strict, I think erring on the side of being more strict is better. This additional check enforces that your promise handler is defined on the parent itself and not calling out to another object.

sudowork · 2017-05-20T16:31:13Z

@bardzusny I've updated this PR to:

No longer require that the call is being made on a method of this
- The rule still enforces that the body of the arrow expression is a CallExpression
Make allowConciseArrow a optional configuration (default: false)
- I'm happy to change the name/format of this option.
- Documented it

michalsnik

Hey @sudowork !

First of all thanks a lot for working on this. It's looking really good :)

Sorry for such late answer but I didn't have much time recently, I left few comments however, check it out and let me know what do you think :)

michalsnik · 2017-05-23T13:03:53Z

lib/rules/named-functions-in-promises.js

@@ -42,5 +47,11 @@ module.exports = {
        utils.isIdentifier(callee.property) &&
        promisesMethods.indexOf(callee.property.name) > -1;
    }
+
+    function isConciseArrowFunctionWithCallExpression(node) {


I'd move this function to utilities, where other functions are, and write unit test for this specific function as well. What do you think?

Will do! I didn't do this at first because I was a bit worried it was too specific.

michalsnik · 2017-05-23T13:06:26Z

tests/lib/rules/named-functions-in-promises.js

+        allowConciseArrow: true,
+      }],
+    }, {
+      code: 'user.save().then(() => user.reload());',


I'm not sure if I agree with this case. I think you should probably write user => this._reloadUser(user) anyway, to be able to test it nicely. What do you think @bardzusny? I see it was like this before but then it was updated..

I was just speaking with @bardzusny and we agreed that in this PR it's ok to allow using xxx.method() to keep it consistent with current regular function expressions that are allowed. We do however think that it might be worth considering in next PR to add additional optional setting called for example requireThisBinding. This setting in practice would force you to use this.method.bind(this) or () => this.method(). I'll create separate issue with this proposition though.

That makes sense to me!

michalsnik · 2017-05-23T13:09:10Z

tests/lib/rules/named-functions-in-promises.js

      parserOptions: { ecmaVersion: 6 },
      errors: [{
        message: 'Use named functions defined on objects to handle promises',
      }],
    }, {
-      code: 'user.save().catch(() => {return error.handle();});',
+      code: 'user.save().finally(() => {return finallyDo();});',


I'd add one or three more tests like this, but with allowConciseArrow set to true just to be totally sure it works like expected :) Of course it should fail then too, because of the arrow function's body not being a CallExpression.

michalsnik · 2017-05-23T13:10:18Z

docs/rules/named-functions-in-promises.md

+
+```
+ember/named-functions-in-promises: [2, {
+  allowConciseArrow: false,


I'm thinking about renaming this setting to allowSimpleArrowFunction - I think it would be more descriptive. What do you think? :)

That sounds good and would probably make more sense to users. I was trying to reuse the language from MDN regarding "concise body".

- Rename `allowConciseArrow` to `allowSimpleArrowFunction` - Update documentation for `allowSimpleArrowFunction` - Move `isConciseArrowFunctionWithCallExpression` to utils - Add unit test for `isConciseArrowFunctionWithCallExpression` - Add invalid test cases for arrow functions with bodies when `allowSimpleArrowFunction` is set to true

sudowork · 2017-05-23T16:41:25Z

@michalsnik Updated to address comments! Thanks for reviewing :)

michalsnik

That was fast! Looks great IMO 🚀 I'll wait for one more approval and then I'll merge this. Thanks for everything @sudowork :)

bardzusny · 2017-05-23T19:10:21Z

tests/lib/utils/utils-test.js

+
+  it('should check if node is concise arrow function expression with call expression body', () => {
+    assert.ok(utils.isConciseArrowFunctionWithCallExpression(node));
+  });


I cannot help but mention that test case for is _not* consise arrow function expression would be nice to have - do you think it's redundant?

In this case it might have a sense indeed. Just to be sure that arrow function with body is not filling requirements of this function. Could you please address that as well @sudowork ? :)

Done @bardzusny @michalsnik 😄 . Added two test cases:

One for arrow using block body

One for concise arrow without a call expression

bardzusny

😍

sudowork added 2 commits May 19, 2017 12:35

Allow concise ArrowFunctionExpression (named-functions-in-promises)

970cb30

Ensure CallExpression is calling a method on the parent object

57b8ceb

This is to ensure that the promise handler is defined as a method on the parent object and not some other object.

sudowork added 4 commits May 19, 2017 13:19

Fix destructuring

148c0d0

Drop requirement that method is called on this

4d01fda

Make allowing concise arrow expressions optional

8cfcdc8

Document allowConciseArrow option (named-functions-in-promises)

997edf8

michalsnik suggested changes May 23, 2017

View reviewed changes

michalsnik added the Work in progress label May 23, 2017

Update isConciseArrowFunctionWithCallExpression test name

c940ab2

michalsnik approved these changes May 23, 2017

View reviewed changes

michalsnik removed the Work in progress label May 23, 2017

bardzusny reviewed May 23, 2017

View reviewed changes

bardzusny approved these changes May 23, 2017

View reviewed changes

Add test case for block body

cbb5d33

michalsnik merged commit 094ef6a into ember-cli:master May 23, 2017

michalsnik mentioned this pull request May 24, 2017

Add optional requireThisBinding in named-functions-in-promises rule #69

Closed

caseywatts mentioned this pull request Aug 9, 2017

named-functions-in-promises example without .bind() #125

Merged

Turbo87 added the Enhancement label Nov 15, 2017

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Allow concise ArrowFunctionExpression (named-functions-in-promises) #64

Allow concise ArrowFunctionExpression (named-functions-in-promises) #64

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Allow concise ArrowFunctionExpression (named-functions-in-promises) #64

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