amoeba commented on code in PR #4939:
URL: https://github.com/apache/arrow-adbc/pull/4939#discussion_r4338752458
##########
r/adbcdrivermanager/R/error.R:
##########
@@ -75,6 +75,16 @@ stop_for_error <- function(status, error) {
# Store the listified error information
cnd$error <- error
+ # R truncates printed error messages to getOption("warning.length")
+ # characters (1000 by default), which cuts off long driver manager
+ # messages such as the list of paths searched for a driver manifest.
+ # Raise the limit to its maximum while the error is signalled so the
+ # full message is shown; the option is restored when stop() unwinds.
+ if (nchar(msg, type = "bytes") > getOption("warning.length", 1000L)) {
+ old_options <- options(warning.length = 8170L)
+ on.exit(options(old_options), add = TRUE)
+ }
+
Review Comment:
There's a slight bug in here. The truncation counts the entire error message
which includes the "Error in adbc_driver("some_driver") :" prefix to `msg`
above. So if we had a 1000-byte msg, I think it would get truncated because R
counts the entire thing.
I think we could just always raise the limit since it's cheap and I don't
think we want to implement the logic to figure out how long the "Error in..."
message will be:
```suggestion
old_options <- options(warning.length = 8170L)
on.exit(options(old_options), add = TRUE)
```
and update the comment above.
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