Copilot instructions

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2applyTo: "src/libraries/Microsoft.Extensions.Logging*/**"
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5# Microsoft.Extensions.Logging — Folder-Specific Guidance
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7## LoggerMessage Source Generator (D16, D13)
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9- `[LoggerMessage]`-attributed methods must be `static partial` — non-static methods cause confusing source generator errors
10- Structured log messages must use template placeholders (`{Name}`) — never embed string interpolation, which bypasses structured logging
11- Log exceptions via the `ILogger` overload that accepts `Exception` as a parameter — do not embed `exception.ToString()` in the template
12- Source-generated logging must produce identical behavior to the runtime logging path — test both paths for parity
13- Generated code must compile without warnings, especially nullable warnings
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15## Log Levels & Security
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17- Never log sensitive data (credentials, tokens, PII, request/response bodies) at any level, including Debug/Trace
18- `IsEnabled` checks should guard expensive log message construction when not using source-generated methods
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20## Error Handling & Diagnostics (D9)
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22- Exceptions from inner operations must be properly wrapped or propagated — do not swallow silently without logging
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24## Logging Provider Configuration
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26- Console formatter behavior and scope inclusion must follow established defaults
27- Changes to provider configuration must not break existing consumer expectations for log output format
28- Logging scope semantics must propagate correctly across async boundaries
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30## Abstractions vs Implementation (D17)
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32- `ILogger`, `ILoggerFactory`, `ILoggerProvider`, and logging attributes belong in `Microsoft.Extensions.Logging.Abstractions`
33- Concrete providers (Console, Debug, EventSource) belong in their respective implementation packages
34- Do not introduce implementation dependencies in the abstractions package
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36## Performance (D5)
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38- Hot logging paths (per-request, per-operation) must use `[LoggerMessage]` source generation for zero-allocation logging
39- Avoid closures that capture state on frequently called log paths — use static lambdas with explicit state
40- String manipulation on log paths must use Span-based APIs to avoid substring allocations
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