DEVNOTES.md

In brodieG/diffobj: Diffs for R Objects

Crayon or Not Crayon

ANSI detection And Settings

Do we want our substring functions to be ansi blind if we detect that the system does not support ansi?

One problem right now is that when in 'raw' mode, we set crayon.enabled=FALSE, but we might still be in a system that supports ANSI and the input itself may have ANSI in it.

Ideally we move away from crayon for ansi detection and rely solely on the style parameter. So probably do that now.

But what about the special case where we are on a system that does not support ANSI escapes, and we want to see the diffs in the ANSI escapes? Do we just not support this?

Probably better to add a separate "ansi.sgr.supported" that for now can default to crayon::has_color()? Then what do we do when someone uses and ANSI style but this is off? Just use it anyway? And provide global nchar and substr functions that are aware of this setting? Yes.

Fansi Problems

Would be great to use fansi instead of crayon for substr as it will be much faster, and also support wide characters, but there are two major issues:

• We still need a terminal ansi-support test, which is well developed and tested in crayon.
• The fansi tests use unitizer, which suggests diffobj; need to check if this actually would cause a circular dependency or not. So diffobj would import fansi, which suggests unitizer. Currently unitizer imports diffobj. So there does seem to be build time circular dependency. We could either change all the fansi tests to not be unitizer (or move the unitizer tests to extra, and have another version of them that tests output with .Rout files). This seems like a massive PITA, and also annoying because we'll need to make sure both sets of tests are run on travis, but not on CRAN, which then makes it hard to make sure we're submitting the same tarball. The more realistic solution might be to remove diffobj as an imports and suggests so that it is possible to build unitizer without diffobj.

Compiled Testing

Run the 'ses' tests with valgrind. They should have 100% coverage of the C code.

We also tracked down these:

==204== Conditional jump or move depends on uninitialised value(s)
==204==    at 0x41E87D7: ???
==204==    by 0xBC983A7: ???
==204==    by 0xBC983A7: ???
==204==    by 0xBC983F9: ???
==204==    by 0x1FFEFF046F: ???
==204==    by 0x2F: ???

To this call:

debug: base::nchar(strip_style(x), ...)
Browse[3]> strip_style(x)
==204== Conditional jump or move depends on uninitialised value(s)
==204==    at 0x41E87D7: ???
==204==    by 0xC6C0E77: ???
==204==    by 0xC6C0E77: ???
==204==    by 0xC6C0E81: ???
==204==    by 0x1FFEFF046F: ???
==204==    by 0x2F: ???

Seems like something funny going on with the perl grep.

That said, we were unable to reproduce by calling gsub directly.

Optim Notes

Using

profvis(for(i in 1:50) as.character(diffPrint(iris, iris.2)))

Getting a bit of time in crayon_strip, surprisingly, but only on the order of 10-15% of total eval time so of limited leverage. Related, nchar_fun as well since it also calls the strip fun.

Some overhead from parameter checks for get_dat that could probably be avoided.

Calls to split/ave also start adding up a bit.

check_args non trivial at about 5% of total exec time.

Calls to head via standardGeneric -> head.default

diff_myers using S4 objects not fantastic.

A bit surprising that the only obvious source of overhead from ansi stuff is the stripping of ansi tags.

Initial conclusion is that there isn't anything super obvious to do here. Faster strip is probably the main improvement, but the rest is just going to be a hard slog of going through a lot of code.

brodieG/diffobj documentation built on June 11, 2025, 3:53 a.m.