shiny::reactiveValues() causes infinite loop

[hadley]

library(shiny)
waldo::compare(reactiveValues(), reactiveValues())
# ... eventually
Error in is_namespaced_call(x) : node stack overflow

[hadley]

Traceback

....
12: compare_by_name(x, y, paths, opts)
11: compare_structure(x_fields, y_fields, paths, opts = opts)
10: compare_structure(x = extract_fun(x, idx[[i]]), y = extract_fun(y, 
        idx[[i]]), paths = c(x_paths[[i]], y_paths[[i]]), opts = opts)
9: compare_by_name(x, y, paths, opts)
8: compare_structure(x_fields, y_fields, paths, opts = opts)
7: compare_structure(x = extract_fun(x, idx[[i]]), y = extract_fun(y, 
       idx[[i]]), paths = c(x_paths[[i]], y_paths[[i]]), opts = opts)
6: compare_by_name(x, y, paths, opts)
5: compare_structure(x_fields, y_fields, paths, opts = opts)
4: compare_structure(x = extract_fun(x, idx[[i]]), y = extract_fun(y, 
       idx[[i]]), paths = c(x_paths[[i]], y_paths[[i]]), opts = opts)
3: compare_by_name(x, y, paths, opts)
2: compare_structure(x, y, paths = c(x_arg, y_arg), opts = opts)
1: waldo::compare(reactiveValues(), reactiveValues())

[hadley]

Inspect the paths reveals the problem:

"new$impl$.allValuesDeps$self$self$self"

[hadley]

Oh because R6 classes are special cased to compare by value, but don't check if they've already seen the environment.