[repo-assist] perf: cache compiled Regex per pattern in JsonSchema.validate

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant.

Problem

JsonSchema.validate constructed a brand-new System.Text.RegularExpressions.Regex on every single string-value validation call when the schema had a pattern constraint:

| Some pattern ->
    let regex = System.Text.RegularExpressions.Regex(pattern)
    ...

For a schema validating many values against the same pattern (e.g. array items, or the same property repeated across many objects), this recompiled the identical regex from scratch on every call — wasted CPU with no benefit, since the pattern string itself never changes for a given schema node.

Fix

Added a small ConcurrentDictionary<string, Regex> cache (patternRegexCache) keyed by the pattern string, with a getPatternRegex helper that compiles a pattern once and reuses it thereafter. validate now calls getPatternRegex pattern instead of constructing a Regex inline.

Rationale / Trade-offs

• No public API or behavior change — same match results, same ValidationResult outputs.
• No new dependencies — System.Collections.Concurrent is part of the BCL.
• Minor, bounded memory cost: one compiled Regex cached per distinct pattern string seen at runtime (schemas typically have a small, fixed set of patterns).
• Thread-safe via ConcurrentDictionary, matching the library's existing use of a Regex per validation call site (previously recreated per-call, now created once).

Test Status

• dotnet run --project build/build.fsproj -t Build: ✅ succeeded, 0 errors (pre-existing warnings only, unrelated to this change)
• dotnet run --project build/build.fsproj -t CheckFormat: ✅ passed ("No files need formatting")
• dotnet test tests/FSharp.Data.Core.Tests/FSharp.Data.Core.Tests.fsproj --filter "FullyQualifiedName~JsonSchema": ✅ 43/43 passed, including validate validates string pattern
• dotnet run --project build/build.fsproj -t RunTests (full suite): ✅ 489 + 3143 + 2 tests passed, 0 failed

Also included

• A RELEASE_NOTES.md entry (8.2.1) documenting the perf fix, per repository conventions.

Warning

Firewall blocked 6 domains

The following domains were blocked by the firewall during workflow execution:

• api.nuget.org
• api.worldbank.org
• dc.services.visualstudio.com
• raw.githubusercontent.com
• schemas.microsoft.com
• tomasp.net

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "api.nuget.org"
    - "api.worldbank.org"
    - "dc.services.visualstudio.com"
    - "raw.githubusercontent.com"
    - "schemas.microsoft.com"
    - "tomasp.net"

See Network Configuration for more information.

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[dsyme]

/repo-assist fix the CI failure due to code formatting here

[github-actions]

✗ Repo Assist encountered failed, see workflow run.

Warning

Firewall blocked 6 domains

The following domains were blocked by the firewall during workflow execution:

• api.nuget.org
• api.worldbank.org
• dc.services.visualstudio.com
• raw.githubusercontent.com
• schemas.microsoft.com
• tomasp.net

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "api.nuget.org"
    - "api.worldbank.org"
    - "dc.services.visualstudio.com"
    - "raw.githubusercontent.com"
    - "schemas.microsoft.com"
    - "tomasp.net"

See Network Configuration for more information.

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[github-actions]

🤖 This is an automated response from Repo Assist.

I investigated the build-ubuntu CI failure (CheckFormat: CsvRuntime.fs needs formatting) reported on attempt 2 of commit 3783699.

Findings — this looks like a transient/flaky failure, not a real formatting issue:

• The independent check-format job on the same commit passed cleanly ("No files need formatting").
• Locally, restoring the exact pinned Fantomas version (7.0.1 from .config/dotnet-tools.json) and running dotnet fantomas <all source files> --check reports "No files need formatting, 0 errored" — CsvRuntime.fs is correctly formatted.
• CsvRuntime.fs at the PR head commit is byte-for-byte identical to the version in the working tree (no CRLF/encoding drift), and passes fantomas --check individually and repeatedly (5/5 runs).

Since I can't reproduce the failure and there's no actual formatting drift to fix, I haven't pushed a code change — that would be an unnecessary/unrelated diff. Re-running the build-ubuntu job should clear it. If it recurs consistently, it may indicate resource contention on the ubuntu-latest runner (fantomas running concurrently with the test build in the same job) rather than a genuine style violation.

Warning

Firewall blocked 6 domains

The following domains were blocked by the firewall during workflow execution:

• api.nuget.org
• api.worldbank.org
• dc.services.visualstudio.com
• raw.githubusercontent.com
• schemas.microsoft.com
• tomasp.net

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "api.nuget.org"
    - "api.worldbank.org"
    - "dc.services.visualstudio.com"
    - "raw.githubusercontent.com"
    - "schemas.microsoft.com"
    - "tomasp.net"

See Network Configuration for more information.

Generated by 🌈 Repo Assist, see workflow run. Learn more.
_{Comment /repo-assist to run again}

_{Add this agentic workflow to your repo}

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/repo-assist.md@5d11aa2a05ce2c943c085acb7b12b583f83ed375