Find $ reads of a partial-matching container — frm_hazard

A testing aid for frmtmb and its extensions, not part of a fitting workflow. It reports every place in a package where $ is used on one of the containers whose slot names collide under partial matching, so an extension can assert in its own test suite that it has none.

Usage

frm_hazard_reads(package)

Arguments

package: A package name, or an environment holding functions (a namespace, which is what a package name resolves to).

Value

A character vector, one entry per read, spelled "function: container$slot", sorted by function name. A package with no hazard read gives character(0).

Details

$ on a list partial-matches: when no name matches exactly, R returns the slot whose name the requested one is a prefix of, rather than NULL. frmtmb keeps several containers whose vocabulary is open (a distributional parameter is named by the user) or prefix-colliding by construction (theta against thetaac, b against beta, se against se_sigma), and a $ read of an absent slot on one of those silently returns a neighbor. [[ returns NULL instead, which is what such call sites assume they are getting.

The rule is keyed on the container's NAME, not on $ in general: fit$obj, x$fit and object$draws are untouched, and a chain is judged one link at a time by its own left-hand name, which is why fit$frame[["par_template"]] is right and fit$frame$par_template is not. The names are therefore RESERVED: binding one of them to something that is not the container it names is itself a hit, and the fix is to rename the local rather than to exempt it.

The scan reads the abstract syntax tree of every function in the namespace, so it sees $ in code and not in a string or a comment, and it works against an installed package, where the sources are no longer on disk. What it cannot see is top-level package code that is not inside a function, because only that code's result is installed.

Examples

# in a package's own test suite:
#   expect_identical(frmtmb::frm_hazard_reads("frmtmb.survival"),
#                    character(0))
frm_hazard_reads("frmtmb")
#> character(0)