Breaking Change: Support ESM

[jeswr]

Breaking changes:

• Files now use named exports rather than default exports
• Deleted MergeIterator which is the same as UnionIterator in AsyncIterator
• Re-organised directory structure; built CJS files are now in dist/ and built ESM files are in esm/
• nestedLoopJoin and dynamicNestedLoopJoin are now functions that use AsyncIterator methods rather than re-implementing existing logic in the AsyncIterator library. These functions could be made even simpler and faster if someone wants to go to the effort of landing this multimap implementation in asynciterator. It may be worth considering the deletion of these two functions from the asyncjoin library entirely.

[jeswr]

Note this devDependency is required to overcome the following error from AsyncIterator.

This may mean that @types/node or @types/event needs to be added to the AsyncIterator dependencies.

$ yarn run build
yarn run v1.22.22
$ npm run build:cjs && npm run build:esm

> asyncjoin@1.2.3 build:cjs
> tsc

join/HashJoin.ts:21:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

21         this.left.on('error', (error) => this.destroy(error));
                     ~~

join/HashJoin.ts:21:32 - error TS7006: Parameter 'error' implicitly has an 'any' type.

21         this.left.on('error', (error) => this.destroy(error));
                                  ~~~~~

join/HashJoin.ts:22:20 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

22         this.right.on('error', (error) => this.destroy(error));
                      ~~

join/HashJoin.ts:22:33 - error TS7006: Parameter 'error' implicitly has an 'any' type.

22         this.right.on('error', (error) => this.destroy(error));
                                   ~~~~~

join/HashJoin.ts:28:24 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

28             this.right.on('readable', () => this.readable = true);
                          ~~

join/HashJoin.ts:29:24 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

29             this.right.on('end', () => { if (!this.hasResults()) this._end(); });
                          ~~

join/HashJoin.ts:32:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

32         this.left.on('end', allowJoining);
                     ~~

join/HashJoin.ts:34:14 - error TS2339: Property 'on' does not exist on type 'HashJoin<S, H, T>'.

34         this.on('newListener', (eventName) =>
                ~~

join/HashJoin.ts:34:33 - error TS7006: Parameter 'eventName' implicitly has an 'any' type.

34         this.on('newListener', (eventName) =>
                                   ~~~~~~~~~

join/HashJoin.ts:43:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

43         this.left.on('readable', () => this._addDataListenerIfNeeded());
                     ~~

join/HashJoin.ts:110:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

110         this.left.on('data', addItem);
                      ~~

join/SymmetricHashJoin.ts:16:14 - error TS2339: Property 'on' does not exist on type 'SymmetricHashJoin<S, H, T>'.

16         this.on('end', () => this._cleanup() );
                ~~

join/SymmetricHashJoin.ts:23:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

23         this.left.on('error', (error) => this.destroy(error));
                     ~~

join/SymmetricHashJoin.ts:23:32 - error TS7006: Parameter 'error' implicitly has an 'any' type.

23         this.left.on('error', (error) => this.destroy(error));
                                  ~~~~~

join/SymmetricHashJoin.ts:24:20 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

24         this.right.on('error', (error) => this.destroy(error));
                      ~~

join/SymmetricHashJoin.ts:24:33 - error TS7006: Parameter 'error' implicitly has an 'any' type.

24         this.right.on('error', (error) => this.destroy(error));
                                   ~~~~~

join/SymmetricHashJoin.ts:26:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

26         this.left.on('readable', () => this.readable = true);
                     ~~

join/SymmetricHashJoin.ts:27:20 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

27         this.right.on('readable', () => this.readable = true);
                      ~~

join/SymmetricHashJoin.ts:30:19 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

30         this.left.on ('end', () => { if (!this.hasResults()) this._end(); });
                     ~~

join/SymmetricHashJoin.ts:31:20 - error TS2339: Property 'on' does not exist on type 'AsyncIterator<S>'.

31         this.right.on('end', () => { if (!this.hasResults()) this._end(); });
                      ~~


Found 20 errors in 2 files.

Errors  Files
    11  join/HashJoin.ts:21
     9  join/SymmetricHashJoin.ts:16

[jeswr]

In fact I'm inclined to go a step further and suggest that this library be deprecated, and that the HashJoin and SymmetricHashJoin be moved into the core of comunica

[rubensworks]

I agree in idea with all of the changes!

nestedLoopJoin and dynamicNestedLoopJoin are now functions that use AsyncIterator methods rather than re-implementing existing logic in the AsyncIterator library. These functions could be made even simpler and faster if someone wants to go to the effort of landing RubenVerborgh/AsyncIterator#50 (comment) in asynciterator. It may be worth considering the deletion of these two functions from the asyncjoin library entirely.

Given the invasiveness of this change, we'll need to have a close look at the impact in comunica performance-wise. Both base comunica and link traversal comunica make very heavy usage of the nested loop join (does not use dynamic nested loop join at all). So even the tiniest change in implementation could have a very big impact on them.

So if you want to have a look at this impact, that would be great, and I can give you instructions.
If not, it might be better if we skip this part of the PR.

[rubensworks]

In fact I'm inclined to go a step further and suggest that this library be deprecated, and that the HashJoin and SymmetricHashJoin be moved into the core of comunica

Sure, that also works :-)