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Support R8 FullMode #1663
Description
Currently Moshi expects JsonAdapters to have the ParameterizedType. But the R8 fullMode (which is enabled by default since AGP8) strips signatures from non-kept items. Therefore the check in parametersAreJsonAdapters (also in the Kotlin implementation) fails because of this assumption and you run into a IllegalArgumentException at runtime.
I was able to fix this by adding the following proguard rule:
-keep,allowobfuscation,allowshrinking class com.squareup.moshi.JsonAdapter
I would expect this rule as part of the META-INF/proguard/moshi.pro
Activity
ZacSweers commentedon Apr 20, 2023
Wanna send a PR? I'd want to see a full description of the implications of that rule and its attributes, but open to it!
G00fY2 commentedon Apr 20, 2023
Currently I just copy pasta this rule from other Android library projects, e.g. this PR which also contains a nice explanation: lysine-dev/retrofit#3579
I think this is also true for Moshi. But I am not really an expert on this topic.
ZacSweers commentedon Apr 20, 2023
Well, PR welcome but would need an explanation of the side effects. We're unlikely to accept a PR with broad proguard/R8 implications without that kind of detail.
DarkAbhi commentedon Apr 27, 2023
G00fY2 commentedon Apr 27, 2023
@DarkAbhi Nope, your stacktrace seems not to be related to Moshi, since it would run into this error: https://github.com/square/moshi/blob/1.14.0/moshi/src/main/java/com/squareup/moshi/AdapterMethodsFactory.java#L226
DarkAbhi commentedon Apr 27, 2023
Right, thanks. I'm going to be running around a lot figuring this out..
DarkAbhi commentedon Apr 27, 2023
Fix 2.5.64 splash crash: disable R8 full mode (Moshi @FromJSON signat…
mvanhorn commentedon Oct 14, 2026
R8 full mode can strip generic signatures from types unmatched by keep rules. Without JsonAdapter's signature, reflection exposes a raw delegate parameter, so Moshi's parameter validation fails and delegate binding cannot recover the type argument.
The embedded R8 rules now match JsonAdapter explicitly to retain its generic signature.
#2139
Fix 2.5.64 splash crash: disable R8 full mode (Moshi @FromJSON signat…