[BUG] Getting an empty knit tries to put
robertc at robertcollins.net
Sun Apr 2 23:47:22 BST 2006
On Sun, 2006-04-02 at 17:56 -0400, Aaron Bentley wrote:
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> Robert Collins wrote:
> | On Fri, 2006-03-31 at 14:48 -0500, Aaron Bentley wrote:
> |>In KnitVersionedFile.__init__, if self.versions() is empty, it will not
> |>only produce a new knit, but attempt to write it to the transport.
> | Right, this is by design: VersionedFiles exist on a persistent storage
> | place.
> So you're saying a VersionedFile must be a representation of a
> physically stored object?
Yes. This is a corollary to the basis of knits or 'revfiles' if we go
back some while where there is a persistent file that we can mutate, and
the in memory representation is typically just the index.
> If that is the case, I think an attempt to get a VersionedFile that
> doesn't exist should throw. But I think it would be a lot nicer if we
> could return an empty versionedfile without having to make it exist on
> physical storage first.
A readonly empty versionedfile would be doable, but ... why ?
> | The bug here is that Repository initialisation is 'lazy' and does not
> | create empty revision, signature knits.
> This is very unexpected behavior to me. An attempt to read should not
> cause an observable write. I think we will continue to have this bug
> appear in various places until we provide a readonly-safe API for
VersionedFile has that api - its VersionedFileStore that is causing the
write request, and thats because get_weave_or_empty was called. If we:
* make the signature and revision files on repo initialisation and
* change fetch to use get_weave()
then no write attempts will be made, and instead it will fail with
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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