Add support for serializing null Instant values in JSON

[mawaelzl]

Description

Fixes NullPointerException when serializing null Instant values
Issue: #765

The solution

null check before calling instant.toString()

Summary by Sourcery

Handle null Instant values during JSON serialization and cover the behavior with a regression test.

Bug Fixes:

• Prevent NullPointerException when serializing null Instant values to JSON.

Tests:

• Add a regression test and approved JSON file to verify serialization of null Instant values.

[sourcery-ai]

Reviewer's Guide

Adds null-safe JSON serialization for java.time.Instant values and introduces a regression test to cover null Instant handling in JsonApprovals.

Class diagram for updated InstantAdapter JSON serialization

classDiagram
  class TypeAdapter_Instant

  class InstantAdapter {
    +write(JsonWriter jsonWriter, Instant instant) void
  }

  class JsonWriter
  class Instant

  TypeAdapter_Instant <|-- InstantAdapter
  InstantAdapter ..> JsonWriter
  InstantAdapter ..> Instant

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Flow diagram for InstantAdapter.write null-safe logic

flowchart TD
  A["start write(JsonWriter jsonWriter, Instant instant)"] --> B{"instant is null"}
  B -->|yes| C["jsonWriter.nullValue"]
  B -->|no| D["jsonWriter.value(concatenate_empty_string_with_instant)"]
  C --> E["end"]
  D --> E["end"]

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File-Level Changes

Change	Details	Files
Make Instant JSON serialization null-safe in JsonUtils.InstantAdapter to avoid NullPointerException.	Update write() to check for null Instant before serialization Write JsonWriter.nullValue() when the Instant is null Serialize non-null Instants via jsonWriter.value("" + instant) instead of instant.toString()	approvaltests-util/src/main/java/com/spun/util/JsonUtils.java
Add regression test ensuring JsonApprovals can serialize objects with null Instant properties.	Import java.time.Instant in JsonApprovalsTest Introduce InstantWrapper test helper with nullable Instant field and getter/setter Add nullInstantTest that verifies JSON output for InstantWrapper using JsonApprovals.verifyAsJson with serializeNulls() Add approved JSON file for nullInstantTest to capture expected serialized form	approvaltests-tests/src/test/java/org/approvaltests/JsonApprovalsTest.java approvaltests-tests/src/test/java/org/approvaltests/JsonApprovalsTest.nullInstantTest.approved.json

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[sourcery-ai]

Hey - I've left some high level feedback:

• In InstantAdapter.write, you can keep using instant.toString() and just guard it with the null check rather than switching to "" + instant, which is less explicit about intent.
• Consider making InstantWrapper a static nested class in JsonApprovalsTest since it doesn’t access any instance state from the outer class and this avoids an unnecessary reference to the test instance.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `InstantAdapter.write`, you can keep using `instant.toString()` and just guard it with the null check rather than switching to `"" + instant`, which is less explicit about intent.
- Consider making `InstantWrapper` a `static` nested class in `JsonApprovalsTest` since it doesn’t access any instance state from the outer class and this avoids an unnecessary reference to the test instance.

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[LarsEckart]

Thank you!