[repo-assist] perf: string/int fast-paths in toParam; StringBuilder+String.Concat in buildXmlDoc#435
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sergey-tihon merged 2 commits intoMay 14, 2026
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…Concat in buildXmlDoc - toParam: add explicit match arms for string, int32, int64, bool to skip GetType() + four type checks (two FullName comparisons, IsGenericType, IsEnum) for the most common OpenAPI scalar parameter types. - buildXmlDoc (Utils.fs): replace list-comprehension + String.concat for paramParts with a StringBuilder loop to avoid F# list cons-cell allocation; replace the final four-way string concatenation with String.Concat(a,b,c,d) to avoid two intermediate string allocations per compiled operation. All 417 unit tests pass. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Two micro-optimizations: a fast path in RuntimeHelpers.toParam for the most common scalar types (string/int32/int64/bool) to avoid reflection, and a StringBuilder/String.Concat rewrite of Utils.buildXmlDoc to reduce intermediate allocations.
Changes:
- Add fast-path match arms for
string,int32,int64,boolintoParambefore the reflective fallback. - Replace list comprehension +
String.concat ""withStringBuilderfor assembling<param>parts inbuildXmlDoc. - Replace chained
+join of XML doc parts withString.Concat4-arg overload.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/SwaggerProvider.Runtime/RuntimeHelpers.fs | Adds scalar-type fast paths in toParam matching prior semantics (uses ToString() like previous fallback). |
| src/SwaggerProvider.DesignTime/Utils.fs | Rewrites paramParts building with StringBuilder and joins final parts via String.Concat. |
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🤖 This PR was created by Repo Assist, an automated AI assistant.
Summary
Two targeted performance improvements identified during routine codebase analysis.
1.
RuntimeHelpers.toParam— fast-path arms for common scalar typestoParamis called for every query parameter, path parameter, and header value in every generated API client call. Previously, all types exceptDateTimeandDateTimeOffsetfell into the catch-all_ ->branch, which:obj.GetType()ty.FullNametodateOnlyTypeNamety.FullNametotimeOnlyTypeNamety.IsGenericTypety.IsEnumobj.ToString()For the most common OpenAPI scalar types —
string,int32,int64, andbool— all five checks are wasted work.Fix: add explicit match arms for these four types, short-circuiting directly to the result:
This avoids
GetType()plus four branch evaluations per call for any parameter of these types.2.
Utils.buildXmlDoc— StringBuilder +String.Concatwith 4 argsbuildXmlDocis called once per compiled operation at design time. Two minor allocations reduced:[ for ... do yield ... ] |> String.concat ""(builds an F# cons-cell list then concatenates) with aStringBuilderloop — no intermediate list allocation.summaryPart + remarksPart + paramParts + returnsPart(two intermediate strings due to left-associative+) withString.Concat(summaryPart, remarksPart, paramParts, returnsPart)— single allocation.Test Status
✅ All 417 unit tests pass
✅ Build succeeds (0 errors, warnings pre-existing)
✅ Fantomas format check passes