We previously had a shallow IsMarked call in compactValueStr's caller but
then a more-conservative deep ContainsMarked call inside compactValueStr
with a different resulting message. As well as causing an inconsistency
in messages, this was also a bit confusing because it made it seem like
a non-sensitive collection containing a sensitive element value was wholly
sensitive, making the debug information in the diagnostic messages not
trustworthy for debugging certain varieties of problem.
I originally considered just removing the redundant check in
compactValueStr here, but ultimately I decided to keep it as a sort of
defense in depth in case a future refactoring disconnects these two
checks. This should also serve as a prompt to someone making later changes
to compactValueStr to think about the implications of sensitive values
in there, which otherwise wouldn't be mentioned at all.
Disclosing information about a collection containing sensitive values is
safe here because compactValueStr only discloses information about the
value's type and element keys, and neither of those can be sensitive in
isolation. (Constructing a map with sensitive keys reduces to a sensitive
overall map.)
This commit adds a comprehensive JSON format for diagnostics, which
ensures that all current diagnostic output can be semantically
represented in a machine-readable format. The diagnostic formatter
interface remains unchanged, but it first transforms its input via the
JSON format to ensure that there is only one code path for creating the
diagnostic data.
The JSON diagnostic renderer extracts the non-presentational logic from
the format package, and returns a structure which can either be
marshaled into JSON or rendered as text. The resulting text diagnostic
output is unchanged for all cases covered by unit tests and my own
manual testing.
Included in this commit are a number of golden reference files for the
marshaled JSON output of a diagnostic. This format should change rarely
if at all, and these are in place to ensure that any changes to the
format are intentional and considered.
Alisdair McDiarmid