Fix NPE

[lmartelli]

Stacktrace from version 23.1.0 :

java.lang.NullPointerException: Cannot invoke "java.util.List.contains(Object)" because "validExtensionsWithDot" is null

	at org.approvaltests.reporters.GenericDiffReporter.isFileExtensionValid(GenericDiffReporter.java:122)
	at org.approvaltests.reporters.GenericDiffReporter.isFileExtensionHandled(GenericDiffReporter.java:117)
	at org.approvaltests.reporters.GenericDiffReporter.isWorkingInThisEnvironment(GenericDiffReporter.java:104)
	at org.approvaltests.reporters.GenericDiffReporter.report(GenericDiffReporter.java:56)
	at org.approvaltests.reporters.FirstWorkingReporter.report(FirstWorkingReporter.java:21)
	at org.approvaltests.reporters.FirstWorkingReporter.report(FirstWorkingReporter.java:21)
	at org.approvaltests.reporters.FirstWorkingReporter.report(FirstWorkingReporter.java:21)
	at org.approvaltests.reporters.FirstWorkingReporter.report(FirstWorkingReporter.java:21)
	at org.approvaltests.approvers.FileApprover.reportFailure(FileApprover.java:49)
	at org.approvaltests.Approvals.verify(Approvals.java:220)
	at org.approvaltests.Approvals.verify(Approvals.java:183)
	at org.approvaltests.Approvals.verify(Approvals.java:191)
	at org.approvaltests.Approvals.verify(Approvals.java:50)

Summary by Sourcery

Bug Fixes:

• Fix the generic diff reporter so configured valid file extensions are retained, preventing a null-pointer exception when validating file extensions.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Fixes the GenericDiffReporter constructor so the provided valid extension list is stored on the instance, preventing the reported NullPointerException when checking whether a file extension is supported.

Sequence diagram for GenericDiffReporter extension validation

sequenceDiagram
    Approvals->>GenericDiffReporter: report()
    GenericDiffReporter->>GenericDiffReporter: isWorkingInThisEnvironment()
    GenericDiffReporter->>GenericDiffReporter: isFileExtensionHandled()
    GenericDiffReporter->>GenericDiffReporter: isFileExtensionValid()
    GenericDiffReporter-->>GenericDiffReporter: validExtensions.contains(extension)
    GenericDiffReporter-->>Approvals: extension support result

Loading

File-Level Changes

Change	Details	Files
Correctly initialize the instance field containing valid file extensions to prevent null access during extension checks.	Replaced assignment to an unqualified symbol with an explicit assignment to the validExtensions field. Ensures isFileExtensionValid can access the constructor-provided extension list.	approvaltests/src/main/java/org/approvaltests/reporters/GenericDiffReporter.java

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[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="approvaltests/src/main/java/org/approvaltests/reporters/GenericDiffReporter.java" line_range="50" />
<code_context>
     this.arguments = argumentsFormat;
     this.diffProgramNotFoundMessage = diffProgramNotFoundMessage;
-    validExtensions = validFileExtensions;
+    this.validExtensions = validFileExtensions;
   }

</code_context>
<issue_to_address>
**issue (bug_risk):** The change is behaviorally identical to the removed assignment and does not prevent `validExtensions` from remaining null. When `validFileExtensions` is null—as permitted by the four-argument constructor and used by existing tests—`isFileExtensionHandled` passes null to `isFileExtensionValid`, whose `contains` call raises the reported NullPointerException.

**Triggers:** When a reporter is constructed with a null extension list.

**Suggested fix:** Default null extension lists to an empty list or handle null in `isFileExtensionHandled`/`isFileExtensionValid`.

```suggestion
    this.validExtensions = validFileExtensions == null ? new ArrayList<String>() : validFileExtensions;
```
</issue_to_address>

Sourcery assessment

Approval pending. 1 finding to address first.

Blocking findings: approvaltests/src/main/java/org/approvaltests/reporters/GenericDiffReporter.java:50

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[sourcery-ai]

issue (bug_risk): The change is behaviorally identical to the removed assignment and does not prevent validExtensions from remaining null. When validFileExtensions is null—as permitted by the four-argument constructor and used by existing tests—isFileExtensionHandled passes null to isFileExtensionValid, whose contains call raises the reported NullPointerException.

Triggers: When a reporter is constructed with a null extension list.

Suggested fix: Default null extension lists to an empty list or handle null in isFileExtensionHandled/isFileExtensionValid.

Suggested change

	this.validExtensions = validFileExtensions;
	this.validExtensions = validFileExtensions == null ? new ArrayList<String>() : validFileExtensions;