Downloaded page/test templates pass constructor argument tuples as one argument

[ugin-man]

On main a72b99f60680ffbe56a4c72e113ca52c9469921e, the generic Download page.tsx and Download test.ts templates serialize the result of getConstructorParams() and pass the entire result as one constructor argument:

const input = [{ limit: 7 }, 3]
const solver = new ProbeSolver(input as any)

For a solver whose original arguments were { limit: 7 }, 3, reconstruction receives [[{ limit: 7 }, 3]] as its argument list instead. The second argument becomes undefined and even a one-element tuple is nested incorrectly.

This is not only a hypothetical tuple convention: the README returns [{ start: this.value, target: this.target }], site/ExamplePipelineSolver.ts returns tuples, and the breadcrumb demo returns [this.params]. The generic templates in lib/react/DownloadDropdown.tsx do not unpack them.

Minimal solver for manual reproduction

class ProbeSolver extends BaseSolver {
  input: { limit: number }
  scale: number
  constructor(input: { limit: number }, scale: number) {
    super()
    this.input = input
    this.scale = scale
  }
  override getConstructorParams() { return [this.input, this.scale] }
  override _step() { this.solved = true }
}

Pass new ProbeSolver({ limit: 7 }, 3) to the downloader and export either generic source template. After resolving the generated project's imports, its construction should restore input.limit === 7 and scale === 3; the current construction gives the tuple to input and leaves scale undefined.

Executed verification

I executed the actual unmodified DownloadDropdown handlers/templates from Git blob e5d0a6a96c71abaccc43ef7820ddaad95e77bb2b, captured their generated Blob text, transpiled it with TypeScript 5.8.3, and executed the generated constructor calls with a probe subclass of the actual BaseSolver. The source blobs were SHA-checked.

Results for both page and test templates:

getConstructorParams result	Expected constructor args	Actual constructor args
[]	[]	[[]]
[{limit:7}]	[{limit:7}]	[[{limit:7}]]
[{limit:7},3]	[{limit:7},3]	[[{limit:7},3]]
[[1,2,3]]	[[1,2,3]]	[[[1,2,3]]]
legacy {limit:7}	[{limit:7}]	[{limit:7}]

Eight tuple cases fail the reconstruction contract; two legacy-object controls pass. Node 22.16.0 was used. React hooks, DOM download plumbing and the generated test's snapshot host were mocked solely to invoke/capture the handlers; this is not a browser-click test or a full generated-project build. The real handler/template strings and constructor invocations were executed without changing their argument logic.

A fix should align generated construction with the tuple convention while deliberately deciding how to preserve legacy plain-object returns. The SchematicTracePipelineSolver-specific page template was not covered by this reproduction. Separate Date-cleanup PR #38 does not change the templates and does not resolve this issue. Prepared with ChatGPT assistance and the account owner's authorization.

[Flame119052]

Fix: #42