fix(promise): don't change source promise

[delagen]

Don't change promise data when caching which cause angular errors in angular-cache project

[codecov-io]

Codecov Report

Merging #30 into master will increase coverage by 0.27%.
The diff coverage is 100%.

@@ Coverage Diff @@## master #30 +/- ##
==========================================
+ Coverage 91.88% 92.15% +0.27% 
==========================================
Files 6 6 Lines 702 701 -1 ==========================================
+ Hits 645 646 +1 + Misses 57 55 -2

Impacted Files	Coverage Δ
src/Cache.js	92.19% <100%> (+0.19%)	✅
src/BinaryHeap.js	90.9% <0%> (+1.01%)	✅

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d31b836...9f72304. Read the comment docs.

[jmdobry]

Can you provide a little more background on the need for this change? Tests?

[delagen]

See angular-cache tests. In case promise stored in cache it also returns as promise till it resolved. Reassign v variable in this case and return breaks original data in promise chain awaiting by angular

[delagen]

See this parts of angular source

if (cache) {
cachedResp = cache.get(url);
if (isDefined(cachedResp)) {
if (isPromiseLike(cachedResp)) {
// cached request has already been sent, but there is no response yet
cachedResp.then(resolvePromiseWithResult, resolvePromiseWithResult);
} else {
// serving from cache
if (isArray(cachedResp)) {
resolvePromise(cachedResp[1], cachedResp[0], shallowCopy(cachedResp[2]), cachedResp[3]);
} else {
resolvePromise(cachedResp, 200, {}, 'OK');
}
}
} else {
// put the promise for the non-transformed response into cache as a placeholder
cache.put(url, promise);
}
}
...
function resolvePromiseWithResult(result) {
resolvePromise(result.data, result.status, shallowCopy(result.headers()), result.statusText);
}

So if cache return something and it's type is PromiseLike so it's parsed as original response (object-like)
otherwise cache object is parsed as stored in cache

In case you change data in then promise pipeline it breaks on result.headers() call

[delagen]

When merge please see my (comment)[https://github.com/jmdobry/angular-cache/issues/224#issuecomment-282945075] which may be fix jmdobry/angular-cache#224

[delagen]

Any news?

[alfaproject]

@jmdobry please? |: