imputesrcref

imputesrcref 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()) and for unbraced function-call arguments. It adds transparent wrappers and imputes srcrefs from parse data so individual 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 target positions to:

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

and:

g({x+1}, {f({y+1})})

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

Exported API

• impute_srcrefs(fn)
  • Impute missing control-flow/function-call 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(imputesrcref.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 -e "testthat::test_check('imputesrcref')"

Refresh snapshots:

UPDATE_SNAPSHOTS=1 Rscript -e "testthat::test_check('imputesrcref')"

By default, mismatches fail. With UPDATE_SNAPSHOTS=1, the snapshot file is rewritten.

Run the optional full ggplot2 package test:

FULL_TEST=1 Rscript -e "testthat::test_check('imputesrcref')"

Acknowledgements

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