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A general description is here.
If ‘--default-packages’ is not used, then ‘Rscript’ now checks the environment variable ‘R_SCRIPT_DEFAULT_PACKAGES’. If this is set, then it takes precedence over ‘R_DEFAULT_PACKAGES’. If default packages are not specified on the command line or by one of these environment variables, then ‘Rscript’ now uses the same default packages as ‘R’. For now, the previous behavior of dropping ‘methods’ can be restored by setting the environment variable ‘R_SCRIPT_LEGACY’ to ‘yes’.
When a package is found more than once, the warning from ‘find.package(*, verbose=TRUE)’ lists all library locations.
‘NAMEDMAX’ has been raised to 3 to allow protection of intermediate results from (usually ill-advised) assignments in arguments to ‘BUILTIN’ functions. Package ‘C’ code using ‘SET_NAMED’ may need to be revised.
Non-UTF-8 multibyte character handling fixed more permanently (PR#16732).