[Rd] suggestion for R >= 3.0: computer-readable CHANGELOG

[Duncan Murdoch]

On 4/17/2009 7:48 AM, ronggui wrote:
> 2009/4/17 Duncan Murdoch <murdoch at stats.uwo.ca>:
>> Philippe Grosjean wrote:
>>>
>>> Hello,
>>>
>>> Here are a few questions that would be useful to get an answer via
>>> dedicated functions in utils or tools packages:
>>> - When did function foo appeared in R or in a given package?
>>> - When did argument myarg appeared in function foo?
>>> - When did function bar get deprecated or when did it disappeared?
>>> - I wrote a script using functions foo and bar with R 1.9.1. My script
>>> does not work any more with current version. What were all the changes made
>>> to foo and/or to bar since then (this could obviously help me to update my
>>> script for current R version)?
>>>
>>> Currently, we have to read NEWS (or perhaps a non official changelog)
>>> manually to get such answers.
>>>
>>> The basic function to retrieve data that would answer to these questions
>>> would be something like:
>>>
>>>  > changes(c("foo", "bar"))
>>>
>>> That function could, for instance, read information in a computer-readable
>>> file named CHANGELOG... because the problem is there! Changes are currently
>>> recorded in NEWS, but ONLY in a human-readable form! A quick suggestion for
>>> a format for CHANGELOG by example:
>>>
>>
>> There is the tools::readNEWS function to read the NEWS file.  It's not just
>> human readable.  That's what the RSS feed uses.
>>>
>>> Date       Object   Action  Value   Message
>>> 2009-04-17 package  commit  1.1-0   Enhanced version of my package
>>> 2009-04-15 foo      add     foo(y)  New function foo in my package
>>> 2009-04-14 bar      debug           bar(NULL) returned wrong result
>>> 2009-04-01 package  commit  1.0-0   First version of package on CRAN
>>>
>>
>> It doesn't contain dates, and dates don't really make sense.  (Many
>> additions are introduced over a sequence of changes.  Do you give the first
>> date, the last date?  What if the change is very minor, e.g. a typo in the
>> docs?)   NEWS does contain R version numbers, and those are well defined.
> 
> Yes. Yet, as the FreeBSD, I found something like "this function first
> appears in R/ foo package  version xxx" in man page helpful. It is not
> bad to put such section in the R help page, I think.

It might be helpful, but often new arguments or changed behaviour happen 
later, so you'd really need a full change history for the function: 
that's what's in the Subversion log, or to some extent, in the NEWS file.

But since we've made an explicit decision not to provide active support 
for older versions, it seems rather pointless to devote extra resources 
to this.  Some new function is only available as of 2.8.0?  Why would 
you care?  You should be using 2.8.1 or 2.9.0 by now.  If you're using 
2.7.1 you're on your own.

Duncan Murdoch

> 
>> The RSS feed does list the date on which it noticed each change to the NEWS
>> file, but I think that is more useful for keeping up to date with changes,
>> rather than defining when something happened.
>>>
>>> It should be kept simple. May be an "Author" field in the records would be
>>> nice too. Also a function to record a new entry in the CHANGELOG could look
>>> like:
>>>
>>
>> Maybe you want the Subversion log.  It is machine readable; just use
>> Subversion to read it.  (Something nice would be R-level access to the
>> Subversion API.) You can be very specific about which files you want to read
>> about, or just read the whole thing on developer.r-project.org.
>>
>> Duncan Murdoch
>>>
>>>  > track("XXX", action = "debug", message = "my comment", file =
>>> "/somewhere/CHANGELOG")
>>>
>>> The file NEWS would not change and should be kept to present the same
>>> information in a human-readable format.
>>>
>>> Also, a function that lists all functions used in a script or a package
>>> (Romain François is working in this direction with svTools package), plus a
>>> function to plot one or several "changes" objects as returned by changes()
>>> on a time axis or "version axis" would be welcome additions to further track
>>> and plot evolution of R, or of R packages for a group of functions of
>>> interest. Finally, a function to easily record the dependences used and
>>> their versions in a script would complete the set of tools.
>>>
>>> These 4-5 functions are not difficult to write (although I suspect that
>>> this simplistic proposal would become more complex if one consider to
>>> interact with subversion, to separate development and release versions,
>>> ...). But to be really useful, they should be better designed and proposed
>>> by the R core team, and included in the official specifications for writing
>>> package. May I suggest to think about such a change for R version 3.0?
>>>
>>> Things get more complicated for verifying CHANGELOG in R CMD check. At
>>> least, one could check actions like:
>>> - object or function addition, deprecation or disappearance,
>>> - argument changes in functions, slot changes in objects,
>>> - function refactoring (change in the code from previous version)
>>> but only if we provide also the previous version of a package to R CMD
>>> check.
>>>
>>> I would be happy to contribute, but the concept must certainly be further
>>> discussed and enhanced (here?), and then, accepted by the R core team before
>>> going any further.
>>>
>>> All the best,
>>>
>>> Philippe Grosjean
>>>
>>
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