Gson 2.11.0

Most important changes

• Added default ProGuard / R8 rules (@Marcono1234, #2397, #2420; @sgjesse, #2448; @sfreilich)
  If you are using ProGuard or R8 (for example for Android projects) you might not need any special Gson configuration anymore if your classes have a no-args constructor and use @SerializedName for their fields.
• On Android, Gson now requires API level 21 or newer
• Added new Strictness API (@marten-voorberg & fellow students, #2437)
  Some of Gson's API is still lenient by default, but you can now use the newly added methods GsonBuilder#setStrictness, JsonReader#setStrictness and JsonWriter#setStrictness with Strictness.STRICT to override this behavior and to instead strictly adhere to the JSON specification when parsing.
• New FormattingStyle class to allow configuring line breaks in JSON output (@mihnita, #2231)
  Can be set using GsonBuilder#setFormattingStyle and JsonWriter#setFormattingStyle.
• TypeToken can no longer capture type variables by default (@Marcono1234, #2376)
  This was previously a common source of issues. The newly thrown exception refers to a Troubleshooting Guide article which explains this in more detail and provides suggestions for updating affected code.
• Added serialization support for anonymous and local classes with a custom adapter (@Marcono1234, #2498)
  This affects for example List implementations returned by libraries such as Guava which are implemented as anonymous class, which were previously serialized as null. Anonymous and local classes without custom adapter will still be serialized as null.
• Added dependency on com.google.errorprone:error_prone_annotations
  Your project can use Maven or Gradle dependency exclusions to remove the transitive error_prone_annotations dependency from Gson. Or if you are manually maintaining dependencies as JARs in your project you can omit error_prone_annotations. And it should still work correctly.
  But Gson itself does declare it as a required dependency, and if you don't perform any custom configuration, then Maven or Gradle will by default try to download and use it.
• Many exception messages now refer to the Troubleshooting Guide (@Marcono1234, #2357)
  Feedback regarding the Troubleshooting Guide is appreciated!
• Officially documented that JVM languages other than Java might not be fully supported, see the README.
• Guarantee that JsonElement#toString produces JSON output (@Marcono1234, #2659)

Other changes

Bug fixes

• Fixed incorrect JsonPrimitive#equals results for large BigInteger values (@MaicolAntali, #2311)
• Fixed incorrect JsonPrimitive#equals results for large BigDecimal values (@MaicolAntali, #2364)
• Fixed JsonReader throwing NumberFormatException instead of MalformedJsonException for malformed Unicode escape sequences (@MaicolAntali, #2337)
• Fixed TypeToken#getParameterized returning bogus ParameterizedType for non-generic types (@Marcono1234, #2447)
• Fixed Java Record adapter not working for GraalVM Native Image (@eamonnmcmanus, #2465)
• Fixed JsonWriter#name not throwing exception when no JSON object is currently being written (@shivam-sehgal, #2475; @Marcono1234, #2476)
• Fixed Gson#getDelegateAdapter not working properly for @JsonAdapter (@Marcono1234, #2435)
  Note that null is now not allowed as skipPast value anymore, which was previously allowed but undocumented.
• Fixed GsonBuilder not rejecting type adapters for Object and JsonElement, whose default adapters cannot be overridden (@sachinp97; #2479)
• Fixed no limits being enforced when deserializing BigDecimal and BigInteger (@Marcono1234, #2510)
  The new limits prevent potential performance problems when user code uses the deserialized numbers. Gson itself was and is not affected by these performance problems. The limits should be high enough to not cause issues for most use cases, but feedback is appreciated.
• Fixed GsonBuilder#setDateFormat not rejecting invalid date formats (@Carpe-Wang, #2538)
• Fixed GsonBuilder#setDateFormat not rejecting invalid date styles (@Marcono1234, #2545)
• Fixed GsonBuilder#setDateFormat ignoring partial DEFAULT style (@Marcono1234, #2556)
• Fixed TypeToken#isAssignableFrom throwing AssertionError in some cases (@Marcono1234, #2544)
• Fixed date adapters not restoring time zone after parsing (@Carpe-Wang, #2549)
• Fixed TypeToken#equals erroneously returning false for equal generic type parameters in some cases (@d-william, #2599)
• Fixed incorrect inherited URLs in pom.xml (@Marcono1234, #2351)

Performance improvements

• Slightly reduce memory usage for reflection-based adapter (@sembseth, #2325; @Marcono1234, #2440)
• Improved parsing speed of ToNumberPolicy#LONG_OR_DOUBLE (@ctasada, #2674)

Gson maintenance

• Changed many unit tests to use Truth instead of JUnit for assertions (@MaicolAntali, #2299, #2304)
• Configured Error Prone to automatically check for bugs when compiling (@MaicolAntali, #2308)
• Simplified expected exception handling in tests (@elevne, #2454)
• Added integration test for GraalVM Native Image (@Marcono1234, #2466)
• Formatted the code according to the Google Style Guide & configured Spotless (@MaicolAntali, #2531, #2537)
• Made Maven build reproducible (@Marcono1234, #2543)
• Removed internal DateTypeAdapter class to reduce code duplication (@Marcono1234, #2546)
• Dependencies and plugins updated by Dependabot

GitHub repository

• Renamed default branch from master to main
• GitHub Discussions have been enabled
  For questions, ideas, tips...
• Added GitHub pull request template (@Marcono1234, #2326)
• Added check for Android API compatibility (@Marcono1234, #2431)

Other

• Added @CanIgnoreReturnValue as appropriate to Gson methods (@eamonnmcmanus, #2369)
  This is useful if you enable Error Prone's CheckReturnValue in your project when compiling, however Gson itself does not enable this by default.
• Various documentation and test improvements and typo fixes (@False-Mask; @avimathur009; @elevne; @0o001; @Codegass; @33nya)

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Many thanks to @Marcono1234 for drafting these release notes.