impuresrcref

impuresrcref imputes transparent srcref metadata for injected brace calls ({) in R function ASTs.

srcref primer

In R, a srcref is source-location metadata (line/column ranges) attached to parsed objects when source retention is enabled (for example with options(keep.source = TRUE)). This package solves a finer-grained mapping problem for control-flow expressions written without braces (for example if (x) f() else g()). It adds transparent wrappers and imputes srcrefs from parse data so individual control-flow components can be mapped to source precisely. It uses the parser token tables getParseData for it.

What it does

Given code like:

if (x && y) f() else g()

impute_srcrefs() rewrites control-flow positions to:

if ({x} && {y}) {f()} else {g()}

and assigns srcrefs to injected { calls using parse-data-derived source spans.

Exported API

• impute_srcrefs(fn)
  • Impute missing control-flow braces and transparent srcrefs for one function.
• source_impute_srcrefs(file, envir = parent.frame(), ...)
  • Source an R file and patch all changed/new functions in the target environment.
• impute_package_srcrefs(package, include_internal = TRUE, ...)
  • Patch package namespace functions if parse data is available

Important: package installs and parse data

For installed packages, parse data is often missing unless the package was installed from source with source/parse retention enabled.

Recommended installation pattern:

    install.packages("<package>", INSTALL_opts=c("--with-keep.source", "--with-keep.parse.data"))

Usage

Patch functions

options(keep.source = TRUE)
f <- eval(parse(text = "function(x, y) if (x && y) f() else g()", keep.source = TRUE)[[1]])
g <- impute_srcrefs(f)
g

Source a file and patch all loaded functions

env <- new.env(parent = baseenv())
res <- source_impute_srcrefs("path/to/file.R", envir = env)
res$functions

Patch an installed package

res <- impute_package_srcrefs("stringr", include_internal = TRUE)
res$patched_count
head(res$failed[!is.na(res$failed)])

Returned fields are:

• package
• fn_names
• failed (NA means successfully patched)
• patched_count
• install_command (reinstall hint when nothing could be patched)

Functions without srcref metadata

impute_srcrefs() requires function srcref metadata by default. For functions created without srcrefs, opt into deparse-based fallback explicitly:

options(impuresrcref.allow_deparse_fallback = TRUE)

Tests

Snapshot tests compare generated output against committed .out golden files. They include regression coverage for:

• package-style srcref line mappings (sr[7:8] vs sr[1:3])
• zero-formals functions (function()) Run tests in compare mode:

Rscript tests/test-srcref-imputation.R

Refresh snapshots:

UPDATE_SNAPSHOTS=1 Rscript tests/test-srcref-imputation.R

By default, mismatches fail. With UPDATE_SNAPSHOTS=1, the snapshot file is rewritten. Legacy --update is still accepted for compatibility.

Acknowledgements

This package was inspired in part by covr's parse-data handling approach.