I have two 1000+ line programs in Perl, each with about 20 subroutines in the main file. One was forked from the other some time ago and I want to factor out the common parts (before porting features backward.) Is there a diff tool that will treat the subroutines (and preceding comments) as units, and extract the common units into a new file? (if one line of a subroutine is different, the unit doesn’t match.)
My SCM is currently Subversion if that helps. A Perl script that processes the code would be cool.
You can try to use the PPI module; to my knowledge there's no tool for refactoring as the one you mentioned.
If you had 500,000 lines of code it might be useful to have or write such a tool. For 1000 lines, this shouldn't be too hard with a simple visual diff tool, like BeyondCompare ($) or WinMerge (free).
You're trying to compare two different versions of the files?
I use VIM which comes with a built in diff program vimdiff and a fully gui one called gvimdiff. It'll fold common lines and just show you the lines that differ and where.
With gvim, you can open up three splits in one window (the two versions and a blank) and then copy over the various lines you want. If you're using Subversion, you can use the built in merge tool (if you're talking about different versions of the same file). The Subversion merge is pretty good and will probably help you with the merge issues.
Related
I have a lot of HTML files (10,000's and GBs worth) scraped from a server and I want to check to make sure the server produces the same results after some modifications but ignore kinds of differences that don't matter, e.g. whitespace, missing newlines, timestamps, small changes in some kinds of number, etc.
Does anyone know of a tool for doing this? I'd really rather not do more filtering than I have to.
(Oh and it needs to run under linux)
You might consider using a clone detector such as our CloneDR. This tool parses large sets of computer program (HTML is special case) files, builds abstract syntax trees representing the essential structure of each files, and compares programs for similarity.
Because it is comparing essential program structure, it ignores inessential differences such as comments and whitespace, and deterimines that two code segments are either identical or one can be obtained from the other by substituting other blocks of code. The latter allows the recognition of code that has been modified in various ways. You can see samples of clone detection runs on a variety of computer languages at the web site.
In your case, what you would be looking for are files in system A which are essentially clones (exact or near misses) of files in system B. As a general rule, if a file a is a variant of file b (e.g., with a few changes) the CloneDr will report it as a clone and show the exact differences.
At the scale of 20,000 files, I can see why you want a tool, and I can see why you want near-miss matches rather than exact matches.
Doesn't run under Linux, but I assume your problem is hard to enough to solve so that isn't what you are optimizing.
I use winmerge alot in windows and from what i can see some people enjoy meld in linux, so perhaps that could do the trick for you
http://meld.sourceforge.net/
Other examples i saw from a quick googling was Kompare,xxdiff.sourceforge.net, and kdiff3.sourceforge.net
(could only post 1 link so wrote the adresses to xxdiff and kdiff3 as text)
Beyond Compare is purchased software that is actually worth the money (I never thought I'd hear myself typing that!). It is GUI based but handles thousands of files very well. It will allow you to specify unimportant changes with regular expressions as well as whitespace (beginning, middle and end of line). The feature set is very extensive, check out a trial download.
I do not work for this company, I just use Beyond Compare every day at work and enjoy it every time!
What source control products have a "diff" facility that ignores white space, braces, etc., in calculating the difference between checked-in versions? I seem to remember that Clearcase's diff did this but Visual SourceSafe (or at least the version I used) did not.
The reason I ask is probably pretty typical. Four perfectly reasonable developers on a team have four entirely different ways of formatting their code. Upon checking out the code last changed by someone else, each will immediately run some kind of program or editor macro to format things the way they like. They make actual code changes. They check-in their changes. They go on vacation. Two days later that program, which had been running fine for two years, blows up. The developer assigned to the bug does a diff between versions and finds 204 differences, only 3 of which are of any significance, because the diff algorithm is lame.
Yes, you can have coding standards. Most everyone finds them dreadful. A solution where everyone can have their cake and eat it too seems far more preferable.
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EDIT: Thanks to everyone for some great suggestions.
What I take away from this is:
(1) A source control system with plug-in type diffs is preferable.
(2) Find a diff with suitable options.
(3) Use a good source formatting program and settle on a check-in standard.
Sounds like a plan. Thanks again.
Git does have these options:
--ignore-space-at-eol
Ignore changes in whitespace at EOL.
-b, --ignore-space-change
Ignore changes in amount of whitespace. This ignores whitespace at line end, and considers all other sequences of one or more
whitespace characters to be equivalent.
-w, --ignore-all-space
Ignore whitespace when comparing lines. This ignores differences even if one line has whitespace where the other line has
none.
I am not sure if brace changes can be ignored using Git's diff.
If it is C/C++ code, you can define Astyle rules and then convert the source code's brace style to the one that you want, using Astyle. A git diff will then produce sane output.
Choose one (dreadful) coding standard, write it down in some official coding standards document, and get on with your life, messing with whitespace is not productive work.
And remember you are a professional developer, it's your job to get the project done, changing anything in the code because of a personal style preference hurts the project - it wont only make diff-ing more difficult, it can also introduce hard to find problems if your source formatter or compiler has bugs (and your fancy diff tool won't save you when two co-worker start fighting over casing).
And if someone just doesn't agree to work with the selected style just remind him (or her) that he is programming as a profession not as an hobby, see http://www.ericsink.com/entries/No_Great_Hackers.html
Maybe you should choose one format and run some indentation tool before checking in so that each person can check out, reformat to his/her own preferences, do the changes, reformat back to the official standard and then check in?
A couple of extra steps but they already use indentation tools when working. Maybe it can be a triggered check-in script?
Edit: this would perhaps also solve the brace problem.
(I haven't tried this solution myself, hence the "perhapes" and "maybes", but I have been in projects with the same problems, and it is a pain to try to go through diffs with hundreds of irrelevant changes that are not limited to whitespace, but includes the formatting itself.)
As explained in Is it possible for git-merge to ignore line-ending differences?, it is more a matter to associate the right diff tool to your favorite VCS, rather than to rely on the right VCS option (even if Git does have some options regarding whitespace, like the one mentioned in Alan's answer, it will always be not as complete as one would like).
DiffMerge is the more complete on those "ignore" options, as it can not only ignore spaces but also other "variations" based on the programming language used in a given file.
Subversion apparently supports this, either natively in the latest versions, or by using an alternate diff like Gnu Diff.
Beyond Compare does this (and much much more) and you can integrate it either in Subversion or Sourcesafe as an external diff tool.
At least two brilliant programmers, Linus Torvalds and Guido von Rossum, disparage the practice of putting keywords into a file that expand to show the version number, last author, etc.
I know how keyword differences clutter up diffs. One of the reasons I like SlickEdit's DiffZilla is because it can be set to skip leading comments.
However, I have vivid memories of team-programming where we had four versions of a file (two different releases, a customer one-off, and the development version) all open for patching at the same time, and was quite helpful to verify with a glance that each time we navigated to an included header we got the proper one, and each time we pasted code the source and destination were what we expected.
There is also the where-did-this-file-come-from problem that arises when a hasty developer copies a file from one place to another using the file system, rather than checking it out of the repository using the tool; or, more defensibly, when files under control in locations A, B, and C need to be marshalled (with cherry-picking) into a distribution location D.
In places where VCS keywords are banned, how do you cope?
I've never used VCS keywords in my entire career, over 30 years. From the most primitive VCS system I've used, up to the present (TFS), I've used some other structure to understand "where I am".
I am rarely in a situation where I've only got one file to work with. I've usually got all the other files necessary to build the project or set of projects. I usually use branching (or streams on one occasion), and I'm working on some slice of the given branch or stream.
If I'm working on multiple branches or streams, I'll have one directory tree for each. All I need to do to know what file I'm working on is check the file path, at the very worst.
At the very best, the version control system will tell you exactly which version of the file you're working on, what the change history is, who else is working on different versions of the file, and anything else you'd care to know.
This doesn't exactly answer your question, but I imagine Linus and Guido have reasons for disliking keywords that don't apply to small-team corporate development.
An $Id$ tag for instance, has what you could consider to be a global version number. Linux and I guess also Python development is fragmented enough that no number can be global. Lots of people have their own repositories all over the place that would fill in their own $Id$ values and then those patches might be sent to Linus or Guido's repositories where they don't make any sense.
However, in your environment, you probably have one central repository which would assign these and it would be fine. Sounds like you're using git. I wonder if it's possible to configure the central git repository to do tag substitution while the local developer repositories don't. Or perhaps it's better to get the commit hash in the tag.
Just trying to get diff to work better for certain kinds of documents. With LaTeX, for example, I might have a long paragraph that is strictly just one line, but I don't want to see that entire paragraph if just a sentence is changed. Particularly if I'm running some kind of version control and a co-author edits the same paragraph (but not the same sentence) as me. I wouldn't want that to show up as a conflict.
That's a secondary question. The main question is whether I can use diff to look sentence-by-sentence. Thanks.
Edit
wdiff is almost perfect. But is there a merge equivalent, as diff has with diff3?
wdiff will give you a word-by-word diff instead of line-by-line. I'm not aware of any sentence-by-sentence diff programs.
Preprocess the files before diffing them. Write a script to write one sentence per line and any line by line diff program will work.
I have done this on a C token level for diffing C code in order to make absolutely sure my CVS merge was correct.
I'm wondering if the need to alter the indentation of code to adjust the nesting has any adverse effects on merging changes in a system like SVN.
I've used python with SVN and Mercurial, and have no hassles merging.
It all depends on how the diffing is done - and I suspect that it is character-by-character, which would notice the difference between one level of indent and another.
It works fine so long as everyone on the project has agreed to use the same whitespace style (spaces or tabs).
But I've seen cases where a developer has converted an entire file from spaces to tabs (I think Eclipse had that as a feature, bound to Ctrl+Tab!), which makes spotting diffs near impossible.
Generally source control systems merge on a line-by-line basis by default. I have found that merging Python code is no different from merging any other source code that is reasonably indented. If one programmer wraps a block of code in an if statement (indenting the whole block), and another programmer modifies something inside the block, then there will be a merge conflict. Fortunately, the conflict in this case is super easy to resolve.
If you use an external merge tool, then your tool may support more detailed textual merging algorithms that take the above scenario into account automatically.