Shim system.file for htmlwidgets so that a dependent package can be used with devtools::load_all()

shim.R

library(inline)

inc <- '
/* This is taken from envir.c in the R 2.15.1 source
   https://github.com/SurajGupta/r-source/blob/master/src/main/envir.c
*/
#define FRAME_LOCK_MASK (1<<14)
#define FRAME_IS_LOCKED(e) (ENVFLAGS(e) & FRAME_LOCK_MASK)
#define UNLOCK_FRAME(e) SET_ENVFLAGS(e, ENVFLAGS(e) & (~ FRAME_LOCK_MASK))
'

src <- '
  if (TYPEOF(env) == NILSXP)
    error("use of NULL environment is defunct");
  if (TYPEOF(env) != ENVSXP)
    error("not an environment");
  UNLOCK_FRAME(env);
  // Return TRUE if unlocked; FALSE otherwise
  SEXP result = PROTECT( Rf_allocVector(LGLSXP, 1) );
  LOGICAL(result)[0] = FRAME_IS_LOCKED(env) == 0;
  UNPROTECT(1);
  return result;
'

unlockEnvironment <- cfunction(signature(env = "environment"),
                        includes = inc,
                        body = src)

imports <- parent.env(asNamespace("htmlwidgets"))
unlockEnvironment(imports)
imports$system.file <- devtools:::shim_system.file


# After the code above has been run, you can load an in-development package
# that uses htmlwidgets (like dygraphs or leaflet). After being loaded this way,
# When the JS or CSS resources of the package are edited, they'll immediately
# be available, without having to build and install the package.
load_all()