man VCP::Maintenance () - VCP code maintenance tips & tricks


VCP::Maintenance - VCP code maintenance tips & tricks




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


The distribution hierarchy

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

   +--- 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
   |  +----  ## dumps files in hex, a debugging aid
   +--+ lib/            ## All modules that comprise VCP itself
   |  +---       ## Drives the VCP process
   |  +--- *.pod        ## Supplemental documentation
   |  +---    ## Base class for all sources & destinations
   |  |
   |  +---    ## Base class for all sources
   |  +--+ Source/
   |  |  +---    ## A backend to read from repo. type "foo"
   |  |
   |  +---      ## Base class for all destinations
   |  +--+ Dest/
   |  |  +---    ## A backend to write to repo. type "foo"
   |  |
   |  +--+ Utils/
   |  |  +---    ## Routines shared by Source/ and Dest/'s
   |  |
   |  +---       ## VCP's concept of a revision
   |  +---      ## 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 CWvcp manually without setting PERL5LIB or installing it.
export PERL5LIB=lib
Allows CWvcp and CWgentrevml to be run from command line
make test
Runs all tests, generating CWt/test-*.revml if need be.

Environment Variables

Some environment variables that are useful in debugging:

Set this to a TRUE value to force CWVCP::* modules emit debugging messages. See also VCP::Debug for more details.
Set this to CWyes to tell CWvcp 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.
Set this to some number from 0..10 to see how CWvcp (via IPC::Run3) is treating it's subprocesses.
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. CWbin/ 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 CWt/90*.t.

The more primitive tests are pretty standard fare for Perl test suites. Where things get interesting is the CWt/90*.t tests. These tests use the command-line CWvcp 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 CWbin/gentrevml is used to generate the RevML files (CWt/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. CWbin/gentrevml should be hacked up to generate these and new rules should be added to the CWMakefile by editing CWMakefile.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 CWsub {...}, every once in a while a single CWsub {...} will contain two tests; it is preceded by an empty (or nearly empty) CWsub {} 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 CWscalar @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 CWmy @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 CWsub 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 CWTEST_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 CW@tests could actually contain just test vectors and the CWfor @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 CWok() would report some line number in the CWfor @tests loop, not the line number of the test.
If you want to enable CWvcp or IPC::Run3 debugging (see VCP::Debug, too), you can put a
   local $ENV{IPCRUN3DEBUG} = 1;  ## 1..10
in the appropriate CWsub {...} 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 CWt/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 CWvcp command can translate from the scheme name (CWcvs:) 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 (CW/lib/

Updating the RevML DTD

Run the command CWcompile_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 CWcompile_dtd.

The generated file is placed in CW./lib/RevML/Doctype/ or CW./RevML/Doctype/ or CW./, 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 CWbin/gentrevml, which is used by the test suite to build the RevML files used for testing.


Barrie Slaymaker <>


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

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