[typescript-fetch] guard required date properties against null

[mvhenten]

A server returns null for a property the schema marks required with format: date. The generated client turns it into 1970-01-01T00:00:00.000Z, a valid Date that flows into business logic unnoticed. An absent value becomes Invalid Date, and serializing that same payload back throws RangeError: Invalid time value.

#24215 added guards for the optional and nullable date cases. Required non-nullable dates were left unguarded; this completes that work.

Required date and date-time are the only property kinds in modelGeneric.mustache that fabricate a value from null. Every other required property passes the raw value through ('x': json['x'], 'x': XFromJSON(json['x'])). Dates now do the same: null stays null, absent stays absent. Passing the value through instead of forcing undefined also keeps the output compiling under strictNullChecks, since json is any and no cast is needed.

A required date arriving as null does violate the schema. The failure mode for that should not be a plausible-looking wrong date.

Generated code

 export function FormatTestFromJSONTyped(json: any, ignoreDiscriminator: boolean): FormatTest {
-        'date': (new Date(json['date'])),
+        'date': (json['date'] == null ? json['date'] : new Date(json['date'])),

 export function FormatTestToJSONTyped(value?: FormatTest | null, ignoreDiscriminator: boolean = false): any {
-        'date': value['date'].toISOString().substring(0,10),
+        'date': value['date'] == null ? value['date'] : value['date'].toISOString().substring(0,10),

Executed behaviour

Client generated from a spec with a required date and a required date-time, run through FromJSON and back through ToJSON:

server response	before	after
{"requiredDate": null}	1970-01-01T00:00:00.000Z → "1970-01-01"	null → null
{}	Invalid Date → throws RangeError: Invalid time value	undefined → undefined
{"requiredDate": "2024-03-05"}	2024-03-05T00:00:00.000Z → "2024-03-05"	unchanged

Optional, nullable and required-nullable dates are unaffected, and both variants typecheck under --strict.

Sample output changes are limited to those four lines in FormatTest (default-v3.0, kebab-case, snakecase-discriminator). No other typescript-fetch sample output changed. TypeScriptFetchClientCodegenTest.testRequiredDatesAreNullGuarded covers the required date-time case, which no existing sample spec exercises.

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/typescript-fetch*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  Commit all changed files.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@leonyu

---

Summary by cubic

Fix null handling for required date and date-time fields in typescript-fetch so null or missing values pass through unchanged, avoiding fabricated dates and runtime errors.

• Bug Fixes
  • Added null guards for required date/date-time in modelGeneric.mustache for both FromJSON and ToJSON.
  • null stays null, absent stays undefined; prevents 1970-01-01T00:00:00.000Z and RangeError: Invalid time value.
  • Added test testRequiredDatesAreNullGuarded and required-date.yaml; updated FormatTest samples only.

^{Written for commit 28165e9. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 6 files

_{Re-trigger cubic}