VCP::Maintenance(3p)

NAME
VCP::Maintenance - VCP code maintenance tips & tricks

SYNOPSIS
 VCPNODELETE=yes

 bin/hexdump.pl

 vcp revml: --dtd <dtd file name> --save_dtd <how>

DESCRIPTION

  The distribution hierarchy
As untarred, the distribution hierarchy looks like (some files not shown for brevity):

   VCP-x.yy/
   +--- Makefile.PL     ## Generates the Makefile
   +--- MANIFEST        ## what files to ship, built with `make manifest`
   +--- MANIFEST.SKIP   ## what filenames `make manifest` should ignore
   +--- CHANGES         ## A detailed summary of all edits
   +--- TODO            ## Things we can't get to quite yet
   +--- LICENSE
   +--- README
   +--- revml.dtd       ## Defines legal RevML
   +--+ bin/            ## Executable files
   |  +---- vcp         ## The command line interface
   |  +---- gentrevml   ## builds RevML files for the test suite
   |  +---- hexdump.pl  ## dumps files in hex, a debugging aid
   |
   +--+ lib/            ## All modules that comprise VCP itself
   |  +--- VCP.pm       ## Drives the VCP process
   |  +--- *.pod        ## Supplemental documentation
   |  +--- Plugin.pm    ## Base class for all sources & destinations
   |  |
   |  +--- Source.pm    ## Base class for all sources
   |  +--+ Source/
   |  |  +--- foo.pm    ## A backend to read from repo. type "foo"
   |  |
   |  +--- Dest.pm      ## Base class for all destinations
   |  +--+ Dest/
   |  |  +--- foo.pm    ## A backend to write to repo. type "foo"
   |  |
   |  +--+ Utils/
   |  |  +--- foo.pm    ## Routines shared by Source/ and Dest/ foo.pm's
   |  |
   |  +--- Rev.pm       ## VCP's concept of a revision
   |  +--- Revs.pm      ## A collection of VCP::Rev instances
   |  |
   |  +--- RevML/       ## Files defining RevML
   |
   +--+ t/              ## The test suite
      +--- *.t          ## Test scripts
      +--- test-*.revml ## Fodder for test scripts

In addition, the following files are created:

   |
   +--- vcp_html        ## By running the `vcp html` command
   +--- pod2htm*        ## Gunk left over from `vcp html`
   +--- blib/           ## By running `make`

  Useful command line idioms

perl -Ilib -cw %
    (in your editor's key mapping).

    Useful to map an editor key to this. Use whatever path for -I works given your cwd usage habit, and replace the "%" with whatever macro your editor replaces with the path to the current file.

make test TEST_FILES=t/90foo.t TEST_VERBOSE=1
    Runs just the listed test files (space separated list; use quotes) and shows STDOUT.

perl -Ilib bin/vcp ...
    Run "vcp" manually without setting PERL5LIB or installing it.

export PERL5LIB=lib
    Allows "vcp" and "gentrevml" to be run from command line

make test
    Runs all tests, generating "t/test-*.revml" if need be.

  Environment Variables
Some environment variables that are useful in debugging:

VCPDEBUG
    Set this to a TRUE value to force "VCP::*" modules emit debugging messages.

    See also VCP::Debug for more details.

VCPNODELETE
    Set this to "yes" to tell "vcp" not to delete it's working directories. This allows you to take a look at them and see what the source and dest command lines saw.

IPCRUN3DEBUG
    Set this to some number from 0..10 to see how "vcp" (via IPC::Run3) is treating it's subprocesses.

VCPP4LICENSE
    If this is present and pointing to a readable file when a p4 daemon is started via vcp, a symlink will be created in the (possibly newly created) p4root directory to point to the p4 license file pointed to by VCPP4LICENSE. The 'make' target test_all_p4_versions will cycle through each version of p4 and p4d contained in the 'p4versions' directory, in both unlicensed and (if VCPP4LICENSE present) licensed mode.

In addition, both CVS and Perforce backends pay attention to the relevant environment variables.

  "hexdump.pl"
"bin/hexdump.pl" is useful for debugging issues involving line endings, embedded control code (esp. ^Z on Win32 and NULL on every platform, since most C programs die when encountering NULL in a text file).

  The tests
The t/*.t files in the source distribution contain a large number of tests. The tests begin with a two digit number that orders them so that more primitive tests run first, followed by higher level "end-to-end" tests in "t/90*.t".

The more primitive tests are pretty standard fare for Perl test suites. Where things get interesting is the "t/90*.t" tests. These tests use the command-line "vcp" interface to move reasonably sized chunks of RevML (up to about 65k currently; pretty small in comparison to "real" exports) in to, out of, and between various repositories.

The RevML extracted from the repositories is compared to the RevML that was fed in to them, after sanitizing both of data that is known to not make it through ok.

The module VCP::TestUtils contains support routines for initializing repositories and shutting them down (when a server is needed). Existing repositories are not used in the test suite; they'd be useless and in danger if we did.

The file "bin/gentrevml" is used to generate the RevML files ("t/test*.revml") from scratch using hand written code instead of VCP::Dest::revml in order to reduce the chances of a bug in VCP::Dest::revml causing false positives in the test results.

It's highly likely that new back ends will require new test RevML files. "bin/gentrevml" should be hacked up to generate these and new rules should be added to the "Makefile" by editing "Makefile.PL".

The structure of a test script.

The t/*.t scripts generally all follow the same structure.

First, they import all necessary modules and init themselves.

Then they build a

   my @tests = (
   sub {
       ...
   },
   );

array that contain the actual tests. Each test is a single anonymous "sub {...}", every once in a while a single "sub {...}" will contain two tests; it is preceded by an empty (or nearly empty) "sub {}" in these cases.

At the bottom, some final checks are run to see if all tests should be skipped, then

   plan tests => scalar @tests;

emits how many tests are to be run, and

   $_->() for @tests;

runs the tests.

This structure is used for several reasons:

1. No counting tests
    Tests are counted automatically for you this way, the "scalar @tests" does this. Otherwise you end up having to remember to manually fudge this every time a test is adding or removed.

2. Clear demarcation
    Tests tend to use local variables a lot; this structure keeps them from "leaking" from one test to another. Things that are shared between tests are usually declared right above the "my @tests =" line and are pretty obvious.

3. Commenting out tests
    In situations where you want to focus on one or a few tests, just put a line like:

        ); @tests = (

    before the first test "sub" you want to run, and a line like

       sub { last },

    after the last one. This is especially important.

4. Test line numbers
    Failing tests, when run with "TEST_VERBOSE=1" as shown above, will report their line numbers. This is the fastest way to find out what's failing. The list-of-subs approach is used even when @tests could actually contain just test vectors and the "for @tests " loop could check the vectors because we want line numbers to tell us where to look. If we used test vectors, then the call to "ok()" would report some line number in the "for @tests" loop, not the line number of the test.

5.  If you want to enable "vcp" or IPC::Run3 debugging (see VCP::Debug, too), you can put a

       local $ENV{IPCRUN3DEBUG} = 1;  ## 1..10

    in the appropriate "sub {...}" and it won't cause all the other tests to spew a lot of noise.

  Developing a new backend
In general, backends are created in pairs so that a "t/90foo.t" can be written to import the RevML files in to the backend repository, extract new RevML from it, and compare the two.

A backend usually consists of 3 Perl classes: VCP::Source::foo, VCP::Dest::foo, and VCP::Utils::foo. The reason for the lowercase final name is so that the "vcp" command can translate from the scheme name ("cvs:") to a source or destination module name trivially.

The VCP::Source::foo generally contains a parser to extract metadata from repository log reports and a routine to drive the copying process. The VCP module ("/lib/VCP.pm")

  Updating the RevML DTD
Run the command "compile_dtd", which by default will look for the file 'revml.dtd'. This should be done each time the dtd changes. Optionally you may pass in a dtd file name as the argument to "compile_dtd".

The generated file is placed in "./lib/RevML/Doctype/" or "./RevML/Doctype/" or "./", whichever is found first. No directories will be created.

This does not update the VCP::Source::revml or VCP::Dest::revml drivers to match the DTD, nor does it affect "bin/gentrevml", which is used by the test suite to build the RevML files used for testing.

AUTHOR
Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT
Copyright (c) 2000, 2001, Perforce Software, Inc. All rights reserved.

See VCP::License ("vcp help license") for the terms of use.