Moshi: NPE on RFC3339DateJsonAdapter when Date is null

[markrebhan]

Discovered this bug while attempting to serialize some JSON with a nullable Date field.

Steps to NPE:

1. Send a null value into RFC3339DateJsonAdapter.toJson()
2. The adapter then sends that null value into ISO8601Utils to be formatted
3. The first thing the format() method does is creates a Calendar and sets the time with a date
4. Calling Calendar.setTime(Date) assumes the date is not null because the first thing it calls is date.getTime() which in this case, throws a NPE

[NightlyNexus]

Call .nullSafe() on the adapter.

[swankjesse]

Any action to take here? Should we document this?

[erikhuizinga]

I would have been helped a lot if this were documented with a short example. I will make a PR for the readme to clarify this feature.

For me as a newcomer to Moshi it took me a while to find this issue, but even the comment mentioning .nullSafe() -- which is the solution -- didn't help me, because I simply didn't understand when or where to use it.

I think with null safety being such a paramount feature of the Kotlin language, you should feature how to work with it in the readme.

[chrisjenx]

Not sure if it's reported else where, but moshi codegen doesn't handle this correctly it will generate:

0 -> timestamp = nullableDateAdapter.fromJson(reader)

When it should generate:

0 -> timestamp = nullableDateAdapter.nullSafe().fromJson(reader)

Is there something I'm missing?

[swankjesse]

Can fix.

[benjamin-bader]

It looks like it's an explicit choice to leave null-checking to installed or generated adapters. Maybe the fix here should go in the RFC3339DateJsonAdapter adapter itself, rather than in generated code?

[ZacSweers]

Seems reasonable. @swankjesse?

On Tue, Jul 16, 2019 at 2:59 PM Ben Bader [e-mail] wrote:

It looks like it's an explicit choice to leave null-checking to installed
or generated adapters. Maybe the fix here should go in the
RFC3339DateJsonAdapter adapter itself, rather than in generated code?

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[ZacSweers]

Opened a PR for this in #910