Non-API calls conundrum

[lionel-]

https://rstudio.github.io/r-manuals/r-exts/The-R-API.html#moving-into-c-api-compliance

Non-problematic:

• SET_ENVFLAGS(): #1705
• R_ClosureExpr() / BODY_EXPR(): Used in r_fn_body(), which is only used in zap_srcref(). Should be fine to call R-level body() instead.

Potentially problematic:

• SET_ENCLOS(): Used to mutate parent environment in quosure evaluation inside data masks. It would be helpful if we could continue to use it to avoid a perf hit when evaluating with many groups. See also https://github.com/r-lib/rlang/issues/1707

Problematic:

• SETLENGTH() / SET_TRUELENGTH(): Used in rlang C API for resizing. Would be nice to get these added to the official API. Also used in vctrs and data.table.

🔥🔥🔥 :

• R_PromiseExpr() / PREXPR(): Essential for tidyeval to access promise expressions. See also https://github.com/r-lib/rlang/issues/1708

[lionel-]

SETLENGTH() / SET_TRUELENGTH(): Used in rlang C API for resizing.

@DavisVaughan proposed to use ALTREP views for resizing to length.

[lionel-]

Found non-API calls to R:

• [x] ENVFLAGS https://github.com/r-lib/rlang/issues/1705
• [x] FRAME https://github.com/r-lib/rlang/pull/1721
• [x] HASHTAB https://github.com/r-lib/rlang/pull/1721
• [x] LEVELS https://github.com/r-lib/rlang/issues/1726
• [x] NAMED https://github.com/r-lib/rlang/commit/5634e9665d056b0e89a3d1a3a52988d85251871a
• [ ] PRENV
• [ ] PRVALUE
• [x] RDEBUG https://github.com/r-lib/rlang/issues/1727
• [ ] R_PromiseExpr,
• [ ] Rf_findVarInFrame3
• [ ] SETLENGTH
• [ ] SET_BODY
• [ ] SET_CLOENV,
• [ ] SET_ENCLOS
• [x] SET_ENVFLAGS https://github.com/r-lib/rlang/issues/1705
• [ ] SET_FORMALS
• [ ] SET_GROWABLE_BIT,
• [x] SET_RDEBUG https://github.com/r-lib/rlang/issues/1727
• [ ] SET_TRUELENGTH
• [ ] SET_TYPEOF
• [ ] STRING_PTR,
• [ ] XTRUELENGTH

[lionel-]

Requests/contribs for R core (WIP):

• [ ] C version of delayedAssign (needed for magrittr placeholder)
• [ ] Predicate to test if a binding is a promise (needed for rlang's env-printer, to prevent arbitrary executions while inspecting envs, etc). Could probably take the form of a "binding type" function that returns an extensible enum.
• [x] To work around LEVELS() in (see rlang https://github.com/r-lib/rlang/issues/1726), a predicate to determine if a CHARSXP is encoded in UTF8. Added in https://github.com/wch/r-source/commit/0c753e41fc06bf5a8825657a5843104a93f28c12
• [ ] Version of getVar() that returns error codes? We either can't afford protecting ourselves from these jumpy R errors, or we'd like to throw our own errors with tailored messages https://github.com/r-devel/r-svn/commit/29a2fda1e9a88a531751cfb908053471533a79c4 Or better, a function that returns the binding type: -> direct, promiseDelayed, promiseForced, active, missing, unbound.

Speculative:

• Iterator for attribute lists, to work around the removal of ATTRIB()? Or at least a way to get the attribute names?