[repo-assist] perf+test: replace UriBuilder+ParseQueryString with StringBuilder; add 9 tests (500→509)

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Summary

Three improvements across runtime performance, test coverage, and code clarity.

Task 8 — Performance: faster query string building

RuntimeHelpers.createHttpRequest previously used UriBuilder + System.Web.HttpUtility.ParseQueryString + NameValueCollection to assemble the query string. This allocates 4–5 objects per API call (UriBuilder, NameValueCollection, internal Hashtable, intermediate strings).

This PR replaces that with a single StringBuilder + Uri.EscapeDataString pass:

// Before (allocates ~5 objects)
let fakeHost = "(fakehost/redacted)
let builder = UriBuilder(combineUrl fakeHost address)
let query = System.Web.HttpUtility.ParseQueryString(builder.Query)
for name, value in queryParams do
    if not <| isNull value then
        query.Add(name, value)
builder.Query <- query.ToString()
builder.Uri.PathAndQuery.TrimStart('/')

// After (allocates 1 StringBuilder)
let sb = Text.StringBuilder(address.TrimStart('/'))
let mutable sep = '?'
for name, value in queryParams do
    if not(isNull value) then
        sb.Append(sep) |> ignore
        sb.Append(Uri.EscapeDataString(name)) |> ignore
        sb.Append('=') |> ignore
        sb.Append(Uri.EscapeDataString(value)) |> ignore
        sep <- '&'
sb.ToString()

The encoding changes from application/x-www-form-urlencoded (+ for spaces) to RFC 3986 percent-encoding (%20 for spaces). Both are accepted by all standards-compliant HTTP servers. The System.Web reference is removed.

Task 5 (fallback for Task 4) — Coding: single-pass toFormUrlEncodedContent

The toFormUrlEncodedContent function previously did two sequential Seq passes (filter then choose). These are merged into a single Seq.choose pass, avoiding an intermediate sequence allocation.

Task 9 — Testing: 9 new tests (500 → 509)

RuntimeHelpersTests (4 tests): document the new RFC 3986 encoding behaviour:

• Spaces in query values are encoded as %20, not +
• Special characters (&, =) in values are percent-encoded
• Special characters in parameter names are percent-encoded
• Multiple query params all encode correctly

Schema.OperationCompilationTests (2 tests): verify 200 response takes priority over 201:

• When both 200 (string) and 201 (integer) responses are defined, 200 wins → Task<string>
• The 201 integer schema is not used

Schema.V2SchemaCompilationTests (4 tests): verify Swagger 2.0 operation return types:

• listPets → Task<Pet[]>
• getPet → Task<Pet>
• getPet path parameter is int64
• createPet → Task<IO.Stream> (documents that Microsoft.OpenApi normalises a v2 201 with no schema to application/octet-stream)

Trade-offs

• %20 vs + for spaces: RFC 3986 is the correct encoding for query components; + is application/x-www-form-urlencoded. Real-world APIs accept both, but %20 is strictly correct for query strings outside of HTML forms.
• StringBuilder pre-allocates no extra capacity — for operations with no query params the result is just the trimmed path (same as the previous fast-path).

Test Status

• dotnet fantomas --check: all files pass ✅
• Unit tests: 509 total, 0 failed, 1 skipped ✅ (up from 500)
• Provider integration tests: not run (require a live test server)

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[Copilot]

Pull request overview

This PR updates the runtime request/query construction logic to reduce allocations, and adds tests that document/verify expected return-type compilation behavior across OpenAPI v3 and Swagger v2 schemas.

Changes:

• Reworked RuntimeHelpers.createHttpRequest query-string assembly to use StringBuilder + Uri.EscapeDataString instead of UriBuilder + ParseQueryString.
• Streamlined toFormUrlEncodedContent to avoid an extra sequence pass.
• Added new unit tests covering query percent-encoding behavior and schema operation return-type selection/priority rules.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/SwaggerProvider.Runtime/RuntimeHelpers.fs	Replaces query-string building implementation and refactors form-url-encoding sequence processing.
tests/SwaggerProvider.Tests/RuntimeHelpersTests.fs	Adds tests asserting RFC3986 percent-encoding behavior for query params.
tests/SwaggerProvider.Tests/Schema.OperationCompilationTests.fs	Adds tests asserting 200 response schema priority over other 2xx responses.
tests/SwaggerProvider.Tests/Schema.V2SchemaCompilationTests.fs	Adds tests validating generated method return types/parameters for a minimal Swagger v2 petstore schema.

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[sergey-tihon]

@copilot address inline comments

[Copilot]

@copilot address inline comments

Addressed in commit 87b3425.

• createHttpRequest now correctly appends parameters when address already has a query string, preserves fragment handling, and keeps the no-added-query fast path allocation-free.
• Added regression tests for existing query (?existing=1) and fragment (#section) scenarios.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.