[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2329: cp -r stops with an exception

[Tahoe-LAFS]

#2329: cp -r stops with an exception
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     Reporter:  zooko    |      Owner:  warner
         Type:  defect   |     Status:  assigned
     Priority:  major    |  Milestone:  1.10.1
    Component:  code-    |    Version:  1.10.0
  frontend-cli           |   Keywords:  regression tahoe-cp review-needed
   Resolution:           |  release-blocker
Launchpad Bug:           |
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Comment (by warner):

 I've got a branch which adds a test that exercises the full table. While
 studying how to change the code to let that test pass, I came across
 another wrinkle: `cp` accepts multiple source arguments.

 In general, if you have multiple source arguments, then the target must be
 a directory. If the target is a directory, then you can't use unnamed
 files as sources (one or multiple). The only case that accepts an unnamed
 file as a source is when you're copying exactly one of them to a target
 that is (or will be) a file.

 Here's a list of what I think should happen (I tried to compress some of
 the cases.. let me know if it doesn't seem to cover everything):


 * sources are NAMEDDIR, UNNAMEDDIR, NAMEDFILE, UNNAMEDFILE
 * targets are DIR, FILE, or MISSING
 * single-source cases:
  * cp FILE TO-FILE: replace the contents
  * cp FILE TO-MISSING: create the target file
  * cp NAMEDFILE TO-DIR: create/replace TO-DIR/filename
  * cp UNNAMEDFILE TO-DIR: error: need a name
  * (cp -r FILE X: behave same as without -r)
  * cp DIR X: error: must use -r if any source is a directory
  * cp -r NAMEDDIR TO-DIR: create TO-DIR/NAME/ and fill with contents
  * cp -r NAMEDDIR TO-MISSING: same: TO-MISSING/NAME/ filled with contents
  * cp -r UNNAMEDDIR TO-DIR: copy source/* into TO/*
  * cp -r UNNAMEDDIR TO-MISSING: same: mkdir TO-MISSING, fill with contents
 * multiple-source cases:
  * cp X.. TO-FILE: error: many-to-one requires target is a directory
  * cp NAMEDFILES.. TO-DIR: create/replace TO-DIR/filenames
  * cp NAMEDFILES.. TO-MISSING: mkdir, then treat like TO-DIR
  * cp UNNAMEDFILES.. X: error: need a name (1 source is ok, but not >1)
  * cp FILESDIRS.. X: error: must use -r if any source is a directory
  * cp -r X.. TO-MISSING: mkdir target, then treat as TO-DIR
  * cp -r X.. TO-DIR:
   * if X is UNNAMEDFILE: error, need a name
   * if X is NAMEDFILE: create/replace TO-DIR/name
   * if X is UNNAMEDDIR: copy source/* into TO/*, like with single-source
   * if X is NAMEDDIR: copy source/* into TO/name/*

 Next step is to figure out how to turn this into a flowchart for
 `tahoe_cp.Copier.try_copy`.. I've started on the internal refactorings to
 make this easier (I was wrong before when I thought the basename should be
 tracked from outside of `TahoeFileSource`/etc.. treating it as a possibly-
 empty property of the source instance is totally the right way to do it).

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2329#comment:40>
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