Hi everyone!
Following the PouchDB discussion[1].
TL;DR we have quite a lot[2] of functions defined in the global
context of executed JS functions (map, show, list, etc.). While
everything is quite simple: read the docs @ use a function, this makes
life harder if you want to write unit tests for your views, run linter
over them and so on and basically everyone around tells you to not
pollute global namespace (:
Another problem with global namespace is that if you call getRow or
send in a map function (yes, you can) - everything will be ruined.
There is no reason for you to do that, but you can and that's an
argument.
Suggestion: deprecate their usage as global things in 2.0 and add one
more argument for each design function (say, ctx) which will be an
object of all valuable helper functions for specific ddoc function.
For instance, map functions will take:
{
'emit': emit,
'JSON': JSON,
'require': require,
'log': log,
'isArray': isArray,
'sum': sum
}
For reduce functions you don't need in emit and require (so far). And
so on. Show/list functions will get their own specific helpers for
sure).
And it will looks like:
function(doc, ctx) {
if (doc.tags && ctx.isArray(doc.tags){
ctx.emit([doc._id, doc.tags]);
}
}
Previously, we had PR[3] to make emit function passed explicitly to
map function. It didn't went too far because it doesn't solves whole
problem.
Also this will simplify a lot Erlang native query server, so we don't
have to use closure hack.
Drawbacks are oblivious:
1. Function signature change
2. We reserve second/third/fifth argument for some service, but very
useful object
I'm not JS expect, but I think it would be better to pass ctx object
as first argument if function accepts two (or three in case of
show/list/update, or five for vdu):
function(doc) { /*old style*/ }
function(ctx, doc) { /*new style*/ }
function(newDoc, oldDoc, secObj, userCtx) { /*old style*/ }
function(ctx, newDoc, oldDoc, secObj, userCtx) { /*new style*/ }
This will make sure that first argument is always an object of
helpers. If we add ctx as the last one, it makes not oblivious since
"last" is different things for each design function.
Anyway, thoughts?
[1]: https://github.com/pouchdb/pouchdb/issues/4624
[2]: http://docs.couchdb.org/en/1.6.1/query-server/javascript.html
[3]: https://github.com/apache/couchdb/pull/127
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,,,^..^,,,
