fix(typescript): dedupe discriminant in generated SSE protocol-union wire tests

[patrickthornton]

Summary

Generated wire tests for SSE endpoints with protocol-discriminated unions previously emitted both an explicit discriminant key and a spread of the deserialized data, which itself already contained the discriminant. Under TypeScript strict, this produced a TS2783: '<field>' is specified more than once, so this usage will be overwritten build error (e.g. auth0/node-auth0#1331).

This PR also fixes a related dead-code bug: the override that promotes a discriminant value from the data payload onto the SSE event: line was running after the discriminant had been deleted from the copy, so it never fired.

Example

For an SSE endpoint with a protocol-discriminated union and an example whose event: line is empty:

- event: ""
  data:
    type: "group.created"
    offset: "offset-1"
    group_id: "g1"

Before:

expect(events).toEqual([
    {
        type: "",                       // TS2783 — overwritten by the spread below
        ...{
            type: "group.created",
            offset: "offset-1",
            group_id: "g1",
        },
    },
]);
// raw response body: 'event: \ndata: {...}\n'  — empty event line

After:

expect(events).toEqual([
    {
        type: "group.created",
        offset: "offset-1",
        group_id: "g1",
    },
]);
// raw response body: 'event: group.created\ndata: {"offset":"offset-1","group_id":"g1"}\n'

The discriminant is now lifted onto the SSE event: line and stripped from data, matching what the runtime SDK's injectDiscriminator produces.

Test plan

• Added a new seed fixture endpoint streamEventsDiscriminantInData in server-sent-event-examples that exercises the empty-event:-line + discriminant-in-data shape.
• Existing streamEventsContextProtocol snapshot loses its redundant event: "completion", ...{event: "completion", ...} wrapper — diff is clean.
• tsc --strict --noEmit on the regenerated completions.test.ts passes (no TS2783).
• pnpm seed test --generator ts-sdk --fixture server-sent-event-examples passes.

🤖 Generated with Claude Code

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SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-04-23T04:59:11Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
csharp-sdk	square	56s (n=5)	86s (n=5)	55s	-1s (-1.8%)
go-sdk	square	115s (n=5)	132s (n=5)	117s	+2s (+1.7%)
java-sdk	square	179s (n=5)	207s (n=5)	188s	+9s (+5.0%)
php-sdk	square	43s (n=5)	66s (n=5)	42s	-1s (-2.3%)
python-sdk	square	115s (n=5)	223s (n=5)	122s	+7s (+6.1%)
ruby-sdk-v2	square	130s (n=5)	159s (n=5)	69s	-61s (-46.9%)
rust-sdk	square	166s (n=5)	163s (n=5)	184s	+18s (+10.8%)
swift-sdk	square	41s (n=5)	290s (n=5)	43s	+2s (+4.9%)
ts-sdk	square	74s (n=5)	86s (n=5)	97s	+23s (+31.1%)

main (generator): generator-only time via --skip-scripts (includes Docker image build, container startup, IR parsing, and code generation — this is the same Docker-based flow customers use via fern generate). main (E2E): full customer-observable time including build/test scripts (nightly baseline, informational). Delta is computed against generator-only baseline.
⚠️ = generation exited with a non-zero exit code (timing may not reflect a successful run).
Baseline from nightly runs on main (latest: 2026-04-23T04:59:11Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-04-29 16:29 UTC

[github-actions]

Docs Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-04-23T04:59:11Z).

Fixture	main	PR	Delta
docs	301.0s (n=5)	298.7s (35 versions)	-2.3s (-0.8%)

Docs generation runs fern generate --docs --preview end-to-end against the benchmark fixture with 35 API versions (each version: markdown processing + OpenAPI-to-IR + FDR upload).
Delta is computed against the nightly baseline on main.
Baseline from nightly run(s) on main (latest: 2026-04-23T04:59:11Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-04-29 16:28 UTC