How can I partially update or merge a list in R? [duplicate]

Question

Here is a R list:

list1 <- list(var1=1,var2=list(var21=1,var22=2,var23=list(var231=1,var232=0)))

Here is another R list:

list2 <- list(var1=3,var2=list(var22=0,var23=list(var232=1,var233=2)),var3=list(var31=1))

Now I want to update list1 by list2, which should include updating existing values and introducing new values. As a result var1, var22, var232should be updated to the value specified in list2, and var233, var3, var31 should be introduced as new entries. Therefore the updated list should be like:

list(var1=3,var2=list(var21=1,var22=0,var23=list(var231=1,var232=2,var233=2)),var3=list(var31=1))

It is very similar with default settings and user-specific settings. The default settings should be loaded and updated by user-specific settings. In my use, I just create a R list from a JSON file (default.json) as default settings and want to update the default settings by another list produced by another JSON file (user.json), like many programs do.

Is there an existing package or some simple/decent way to do this?

Answer 1

There's a modifyList for these purposes. Note that I corrected list3 definition, there's a mistake in your desired output.

list4 <- modifyList(list1, list2)
list3 <- list(var1=3,var2=list(var21=1,var22=0,var23=list(var231=1,var232=1,var233=2)),var3=list(var31=1))
all.equal(list3, list4)
[1] TRUE