Add recovery package with panic recovery middleware

recovery/doc.go

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+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package recovery provides panic recovery middleware for HTTP handlers.
+//
+// The middleware recovers from panics in HTTP handlers and returns a
+// 500 Internal Server Error response to the client. This prevents a single
+// panicking request from crashing the entire server.
+//
+// # Basic Usage
+//
+//	mux := http.NewServeMux()
+//	mux.HandleFunc("/", handler)
+//	wrappedMux := recovery.Middleware(mux)
+//	http.ListenAndServe(":8080", wrappedMux)
+//
+// # Stability
+//
+// This package is Beta stability. The API may have minor changes before
+// reaching stable status in v1.0.0.
+package recovery

recovery/recovery.go

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+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package recovery
+
+import (
+	"net/http"
+)
+
+// Middleware is an HTTP middleware that recovers from panics.
+// When a panic occurs, it returns a 500 Internal Server Error response
+// to the client, preventing the panic from crashing the server.
+//
+// TODO(#7): Add configurable logging support once common logging is
+// established across ToolHive. Currently panics are silently recovered.
+func Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer func() {
+			if recover() != nil {
+				// TODO(#7): Log panic value and stack trace
+				// stack := debug.Stack()
+				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
+			}
+		}()
+		next.ServeHTTP(w, r)
+	})
+}

recovery/recovery_test.go

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+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package recovery
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMiddleware_NoPanic(t *testing.T) {
+	t.Parallel()
+
+	// Create a test handler that does not panic
+	testHandler := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("success"))
+	})
+
+	// Wrap with recovery middleware
+	wrappedHandler := Middleware(testHandler)
+
+	// Create test request
+	req := httptest.NewRequest(http.MethodGet, "/test", nil)
+	rec := httptest.NewRecorder()
+
+	// Execute request
+	wrappedHandler.ServeHTTP(rec, req)
+
+	// Verify response
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Equal(t, "success", rec.Body.String())
+}
+
+func TestMiddleware_RecoverFromPanic(t *testing.T) {
+	t.Parallel()
+
+	// Create a test handler that panics
+	testHandler := http.HandlerFunc(func(_ http.ResponseWriter, _ *http.Request) {
+		panic("test panic")
+	})
+
+	// Wrap with recovery middleware
+	wrappedHandler := Middleware(testHandler)
+
+	// Create test request
+	req := httptest.NewRequest(http.MethodGet, "/test", nil)
+	rec := httptest.NewRecorder()
+
+	// Execute request - should not panic
+	wrappedHandler.ServeHTTP(rec, req)
+
+	// Verify 500 Internal Server Error response
+	assert.Equal(t, http.StatusInternalServerError, rec.Code)
+	assert.Contains(t, rec.Body.String(), "Internal Server Error")
+}
+
+func TestMiddleware_PreservesRequestContext(t *testing.T) {
+	t.Parallel()
+
+	type contextKey string
+	const key contextKey = "test-key"
+	const value = "test-value"
+
+	var receivedValue string
+
+	// Create a test handler that reads from context
+	testHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if v := r.Context().Value(key); v != nil {
+			receivedValue = v.(string)
+		}
+		w.WriteHeader(http.StatusOK)
+	})
+
+	// Wrap with recovery middleware
+	wrappedHandler := Middleware(testHandler)
+
+	// Create test request with context value
+	req := httptest.NewRequest(http.MethodGet, "/test", nil)
+	ctx := context.WithValue(req.Context(), key, value)
+	req = req.WithContext(ctx)
+	rec := httptest.NewRecorder()
+
+	// Execute request
+	wrappedHandler.ServeHTTP(rec, req)
+
+	// Verify context was preserved
+	assert.Equal(t, http.StatusOK, rec.Code)
+	assert.Equal(t, value, receivedValue)
+}