Check whether already-split .from/.to/.weight_by columns form a valid crossmap (internal)

The single source of truth for the three link-validity conditions, shared by validate_as_xmap.data.frame() and xmap_tbl()'s construction gate, so the two don't independently re-implement (and risk drifting on) the same checks.

Usage

check_valid_xmap_df(tbl_x, tol)

Arguments

tbl_x

A tibble/data frame with .from, .to, .weight_by columns (each may themselves be single-column data frames, as xmap_tbl stores them).

tol

Deliberately has no default here, unlike the exported entry points that call this – forces every caller to explicitly forward its own user-facing tol rather than one silently drifting to an unexposed internal default if a future edit forgets to pass it through.

Value

A single logical.