fix(generate): send present but falsy optional values as present

[marc0olo]

Bottom of a two-PR stack (#198 builds on it) fixing conversions that are silently wrong.

Behaviour

This changes what goes on the wire. A canister that received nothing for these values now receives what the caller asked to send.

you write	you mean	before	after
record field { count: 0n } (opt nat)	present, value 0	[], absent	[0n]
record field { flag: false }, { name: "" }	present	[]	[false], [""]
record field omitted or undefined	absent	[]	[]
variant payload { __kind__: "count", count: 0n }	present, value 0	{ count: [] }	{ count: [0n] }
variant payload count: null	absent	{ count: [] }	{ count: [] }
bare opt argument 0n	present	[0n]	[0n], unchanged

Why

Optional record fields and variant payloads were encoded with a truthiness test (value.count ? candid_some(…) : candid_none()), so 0, false and "" could not be sent at all. The generated code was valid and typechecked, which is why snapshots and typechecks passed over it. The test is now != null; bare opt arguments already compared with null.

Testing

tests/conversion.test.ts generates the bindings, calls the generated wrapper with a stub actor and checks what reaches it. It fails on main with expected { count: [] } to deeply equal { count: [ 0n ] }. tests/utils/wrapper.ts loads the wrapper against a minimal @icp-sdk/core stub. The snapshot changes are the example fixture's two optional fields.

🤖 Generated with Claude Code

[Copilot]

Copilot review overview

🟡 Changes recommended

Repeated wrapper calls overwrite cleanup state and leak temporary directories.

Review effort: Balanced
Findings: 1

Open (1)

• Repeated sentBy calls leak temporary directories · New

What changed in this PR

Corrects TypeScript-to-Candid conversion so falsy optional values remain present.

Changes:

• Replaces truthiness checks with nullish presence checks.
• Adds runtime conversion tests and supporting fixtures.
• Updates generated snapshots.

File	Description
src/​core/​generate/​rs/​src/​bindings/​typescript_native/​conversion_functions_generator.rs	Generates nullish optional checks.
tests/​conversion.test.ts	Tests optional-value conversion.
tests/​utils/​wrapper.ts	Loads generated wrappers with stub dependencies.
tests/​assets/​optional_presence.did	Defines optional conversion fixtures.
tests/​snapshots/​generate/​example/​example.ts.snapshot	Updates generated output.
tests/​snapshots/​wasm-generate/​no-root-export/​example/​example.ts.snapshot	Updates no-root-export output.
tests/​snapshots/​wasm-generate/​root-export/​example/​example.ts.snapshot	Updates root-export output.
tests/​snapshots/​wasm-generate/​typescript/​example/​example.ts.snapshot	Updates TypeScript output.
tests/​snapshots/​wasm-generate/​typescript-root-export/​example/​example.ts.snapshot	Updates TypeScript root-export output.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The focused generator fix correctly preserves falsy values and is covered by runtime tests and snapshots.

Review effort: Balanced
Findings: None

Resolved since last review (1)

• Repeated sentBy calls leak temporary directories