Give every Firestore DTO a no-arg constructor (Track C blocker)

[Quasar-Apps-Agent]

Track C item 1 — the blocker that gates the rest of Track C.

The bug

Firestore's object mapper instantiates targets reflectively via toObject() / toObjects(), which requires a public no-arg constructor. Kotlin only emits one for a data class when every primary-constructor parameter has a default.

All 15 *Dto types in IBackendService.kt had at least one parameter without a default, so none was constructible. FirebaseBackendService calls toObject/toObjects 26 times, and its firestoreCall wrapper swallows the throw into Result.Error. Writes succeeded; reads all failed silently.

Net effect: flipping USE_MOCK_BACKEND=false produced a write-only app. This is item 1 of Track C because nothing else in Track C — the 14 stubs, security rules, profile-doc creation — is even observable against a real Firestore until reads work.

The fix

A type-appropriate default on the 114 parameters that lacked one, across all 15 *Dto types ("", 0, 0.0, 0f, false, emptyList(), null for nullables).

The 10 *Request types are deliberately unchanged — they're only ever written, never deserialized, so required parameters there remain a genuine safety net. Verified the diff touches only *Dto classes: all 114 changed lines map to the 15 DTOs, zero to *Request.

All existing construction sites use named arguments, so none is affected.

Regression guard

FirestoreDtoContractTest encodes the contract without needing Firebase:

• every DTO exposes a public no-arg constructor
• invoking it actually succeeds (newInstance(), not just getDeclaredConstructor())
• the registered list stays in sync with the source

These fail the moment someone removes a default — precisely the change that would silently break reads again.

Known tradeoff — stated rather than buried

These DTOs are also @Serializable, and SyncManager decodes BookingDto/ServiceDto/ClientDto from queued payloads (SyncManager.kt:250,292,305). kotlinx previously threw MissingFieldException when a payload was missing a required field, surfacing as a FAILED op; it will now fall back to the default instead.

That trades strictness for deserializability, and it's the same fail-loudly-vs-silently concern #19–#21 were about, so I won't pretend it isn't there. It has no live impact today — queueOperation still has zero production callers — but if the queue is ever wired, mapper-level validation should replace the strictness this gives up.

The alternative (keep DTOs strict, hand-write 15 DocumentSnapshot mappers) avoids that but adds ~150 lines of boilerplate and its own bug surface. TECH_LEAD_REVIEW.md §9.4 lists the defaults approach as the recommended option; happy to revisit if you'd prefer the mappers.

Verification

No Android SDK locally, so CI is the check. Verified by inspection and scripted analysis: 15/15 DTOs now have all-default parameters, 0 *Request classes touched, parens/braces balanced, no mangled call sites, and every DTO named in the test cross-checked against the source declarations (15 declared, 15 referenced, 0 missing, 0 bogus).

🤖 Generated with Claude Code

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Generated by Claude Code

[Copilot]

Pull request overview

Enables successful Firestore deserialization against the real backend by ensuring every Firestore-read DTO is reflectively constructible (public no-arg constructor), and adds a JVM-only contract test to prevent regressions.

Changes:

• Added type-appropriate default values to all primary-constructor parameters across the 15 *Dto types in IBackendService.kt so Kotlin emits a public no-arg constructor.
• Added FirestoreDtoContractTest to assert the no-arg constructor exists, is public, and is invokable via Java reflection.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
data/src/main/java/com/example/diamonds/data/remote/backend/IBackendService.kt	Makes all Firestore DTOs default-constructible by providing defaults for previously-required constructor parameters.
data/src/test/java/com/example/diamonds/data/remote/backend/FirestoreDtoContractTest.kt	Adds reflection-based tests intended to guard the Firestore DTO no-arg-constructor contract.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Suppressed comments (1)

data/src/test/java/com/example/diamonds/data/remote/backend/FirestoreDtoContractTest.kt:125

• DTO_DECLARATION is currently anchored to ^data class ...(, so it will miss valid Kotlin declarations that have leading whitespace or a visibility modifier (e.g., internal data class FooDto(). In that case a new DTO could be added without being detected, and this guard would silently pass.

    private companion object {
        val DTO_DECLARATION = Regex("""^data class (\w+Dto)\(""", RegexOption.MULTILINE)
    }