blockstore: skip location for memory store

[tuxcanfly]

While here, fix docs examples which were failing due to improperly configured blockstore.

Also a minor nit: new bcoin.Chain() instantiates a new Chain without a blockstore, since options is null. This is because we only validate options if they are given, but if given we require a blockstore (except in spv). We could add another check if options is null. Thoughts?

[pinheadmz]

Encountered the same thing writing #832.

Chain doesn't seem to use memory. Meanwhile, creating a Blockstore is different from kinda every other module in bcoin, in that new Blockstore({memory: true}) is not valid, and LevelBlockStore requires a location, even if memory: true

[braydonf]

Yeah, location isn't necessary in the memory case of blockstore.create.

I still think it would be better to have the examples show usage of persisting data, since that is a common case. This includes use of ensure and similar. That is probably for another PR, this is closer to current usage by a node.

[braydonf]

@tuxcanfly

new bcoin.Chain()

Should likely remove the if (options) from lib/blockchain/chain:

if (options)
  this.fromOptions(options)

[braydonf]

@pinheadmz

Chain doesn't seem to use memory.

If you grep for memory in lib/blockchain/chain.js and lib/blockchain/chaindb for usage you won't find it, however memory is still an option used for the database in ChainDB of Chain.

...creating a Blockstore...

That isn't a class, there is AbstractBlockStore, FileBlockStore and LevelBlockStore, and as detailed a blockstore.create function, as similar to the function for creating a bdb database.

[pinheadmz]

@braydonf

I still think it would be better to have the examples show usage of persisting data, since that is a common case.

One thing I like about the examples is that they can just be run in place and show the user some quick output without writing temp junk to disk. Should we add an example demonstrating bcoin's usage of filesystem (including ensure(), etc)?

As discussed in #832 maybe we should just get rid of the docs/Examples entirely, move it to bcoin.io/guides or something? Issues like #831 are popping up as users try to base production code off the examples...

[tuxcanfly]

@pinheadmz Like this PR (and yours) bought to notice - sometimes minor config changes creep without us noticing (especially around larger PRs like blockstore). So the examples are a rather nice way of testing bcoin clients and making sure none of the moving parts break. If we end up retaining them maybe we could have CI run them and check their exit code, just to see that they're working as intended (such a CI task would have caught this issue much earlier).