If you can afford a dependency on rlang, `rlang::zap_srcref()` deals with this. It's recursive over expression vectors, calls (including calls to `function` and their hidden srcref arg), and function objects. It's implemented in C for efficiency as we found it to be a bottleneck in some applications (IIRC caching). I'd be happy to upstream this in base if R core is interested.
Best, Lionel On 3/30/23, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 30/03/2023 10:32 a.m., Ivan Krylov wrote: >> Dear R-devel, >> >> In a package of mine, I use removeSource on expression objects in order >> to make expressions that are semantically the same serialize to the >> same byte sequences: >> https://github.com/cran/depcache/blob/854d68a/R/fixup.R#L8-L34 >> >> Today I learned that expressions containing function definitions also >> contain the source references for the functions, not as an attribute, >> but as a separate argument to the `function` call: >> >> str(quote(function() NULL)[[4]]) >> # 'srcref' int [1:8] 1 11 1 25 11 25 1 1 >> # - attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' >> # <environment:0x55aba55a8a50> >> >> This means that removeSource() on an expression that would define a >> function when evaluated doesn't actually remove the source reference >> from the object. >> >> Do you think it would be appropriate to teach removeSource() to remove >> such source references? What could be a good way to implement that? >> if (is.call(fn) && identical(fn[[1]], 'function')) fn[[4]] <- NULL >> sounds too arbitrary. if (inherits(fn, 'srcref')) return(NULL) sounds >> too broad. >> > > I don't think there's a simple way to do that. Functions can define > functions within themselves. If you're talking about code that was > constructed by messing with language objects, it could contain both > function objects and calls to `function` to construct them. You'd need > to recurse through all expressions in the object. Some of those > expressions might be environments, so your changes could leak out of the > function you're working on. > > Things are simpler if you know the expression is the unmodified result > of parsing source code, but if you know that, wouldn't you usually be > able to control things by setting keep.source = FALSE? > > Maybe a workable solution is something like parse(deparse(expr, control > = "exact"), keep.source = FALSE). Wouldn't work on environments or > various exotic types, but would probably warn you if it wasn't working. > > Duncan Murdoch > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
