[TT-14666] gw panics after updating from 5 0 with oas api (#7046)

<details open>
<summary><a href="https://tyktech.atlassian.net/browse/TT-14666"
title="TT-14666" target="_blank">TT-14666</a></summary>
  <br />
  <table>
    <tr>
      <th>Summary</th>
      <td>GW panics after updating from 5.0 with OAS API</td>
    </tr>
    <tr>
      <th>Type</th>
      <td>
<img alt="Bug"
src="https://tyktech.atlassian.net/rest/api/2/universal_avatar/view/type/issuetype/avatar/10303?size=medium"
/>
        Bug
      </td>
    </tr>
    <tr>
      <th>Status</th>
      <td>In Dev</td>
    </tr>
    <tr>
      <th>Points</th>
      <td>N/A</td>
    </tr>
    <tr>
      <th>Labels</th>
<td><a
href="https://tyktech.atlassian.net/issues?jql=project%20%3D%20TT%20AND%20labels%20%3D%20QA_Fail%20ORDER%20BY%20created%20DESC"
title="QA_Fail">QA_Fail</a></td>
    </tr>
  </table>
</details>
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---

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## Description

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## Related Issue

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issue first. -->
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## Motivation and Context

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## How This Has Been Tested

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## Types of changes

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the boxes that apply: -->

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Refactoring or add test (improvements in base code or adds test
coverage to functionality)

## Checklist

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that apply -->
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checked. -->
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- [ ] I ensured that the documentation is up to date
- [ ] I explained why this PR updates go.mod in detail with reasoning
why it's required
- [ ] I would like a code coverage CI quality gate exception and have
explained why

Author: andrei-tyk

gateway/api_loader.go

@@ -800,10 +800,6 @@ func (gw *Gateway) loadHTTPService(spec *APISpec, apisByListen map[string]int, g
 		chainObj = gw.processSpec(spec, apisByListen, gs, logrus.NewEntry(log))
 	}
 
-	if chainObj == nil {
-		return nil, fmt.Errorf("trying to import invalid api %s, skipping", spec.APIID)
-	}
-
 	if chainObj.Skip {
 		return chainObj, nil
 	}
@@ -1007,7 +1003,9 @@ func (gw *Gateway) loadApps(specs []*APISpec) {
 			defer func() {
 				// recover from panic if one occurred. Set err to nil otherwise.
 				if err := recover(); err != nil {
-					log.Errorf("Panic while loading an API: %v, panic: %v, stacktrace: %v", spec.APIDefinition, err, string(debug.Stack()))
+					if err := recoverFromLoadApiPanic(spec, err); err != nil {
+						log.Error(err)
+					}
 				}
 			}()
 
@@ -1102,6 +1100,13 @@ func (gw *Gateway) loadApps(specs []*APISpec) {
 	}
 }
 
+func recoverFromLoadApiPanic(spec *APISpec, err any) error {
+	if spec.APIDefinition.IsOAS && spec.OAS.GetTykExtension() == nil {
+		return fmt.Errorf("trying to import invalid OAS api %s, skipping", spec.APIID)
+	}
+	return fmt.Errorf("Panic while loading an API: %v, panic: %v, stacktrace: %v", spec.APIDefinition, err, string(debug.Stack()))
+}
+
 func (gw *Gateway) allApisAreMTLS() bool {
 	gw.apisMu.RLock()
 	defer gw.apisMu.RUnlock()

gateway/api_loader_test.go

@@ -10,17 +10,17 @@ import (
 	"path"
 	_ "path"
 	"reflect"
-	"sync"
+	"strings"
 	"sync/atomic"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 
 	persistentmodel "github.com/TykTechnologies/storage/persistent/model"
 	"github.com/TykTechnologies/tyk/apidef"
+	"github.com/TykTechnologies/tyk/apidef/oas"
 	"github.com/TykTechnologies/tyk/config"
 	"github.com/TykTechnologies/tyk/internal/uuid"
-	"github.com/TykTechnologies/tyk/storage"
 	"github.com/TykTechnologies/tyk/test"
 	"github.com/TykTechnologies/tyk/trace"
 	"github.com/TykTechnologies/tyk/user"
@@ -9627,94 +9627,36 @@ func TestSortSpecsByListenPath(t *testing.T) {
 	}
 }
 
-func TestForTyk5OasMigration(t *testing.T) {
-	g := StartTest(nil)
-	defer g.Close()
-
-	internal := BuildAPI(func(spec *APISpec) {
-		spec.OAS.Extensions = nil
-		spec.IsOAS = true
-		spec.VersionData.Versions = map[string]apidef.VersionInfo{"a": {ExtendedPaths: apidef.ExtendedPathsSet{ValidateRequest: []apidef.ValidateRequestMeta{{Enabled: true}}}}}
-		spec.Name = "test-for-legacy-oas"
-		spec.APIID = "test-legacy-oas-api-id"
-		spec.Proxy.ListenPath = "/test-for-legacy-oas"
-		spec.AuthManager = MockSessionHandler{}
-		spec.Health = MockHealthChecker{}
-		spec.OrgSessionManager = MockSessionHandler{}
-	})[0]
-
-	g.Gw.apisMu.Lock()
-	g.Gw.apisByID[internal.APIID] = internal
-	g.Gw.apisMu.Unlock()
-
-	if g.Gw.apisHandlesByID == nil {
-		g.Gw.apisHandlesByID = new(sync.Map)
+func TestRecoverFromLoadApiPanic(t *testing.T) {
+	tests := []struct {
+		name     string
+		spec     *APISpec
+		err      any
+		expected string
+	}{
+		{
+			name: "invalid OAS api",
+			spec: &APISpec{
+				APIDefinition: &apidef.APIDefinition{
+					APIID: "test-api",
+					IsOAS: true,
+				},
+				OAS: oas.OAS{},
+			},
+			err:      "test error",
+			expected: "trying to import invalid OAS api test-api, skipping",
+		},
 	}
-	g.Gw.apisHandlesByID.Delete(internal.APIID)
-
-	apiByListenPath := map[string]int{}
-
-	_, err := g.Gw.loadHTTPService(internal, apiByListenPath, &generalStores{}, &proxyMux{})
-
-	assert.Equal(t, fmt.Sprint(err.Error()), "trying to import invalid api test-legacy-oas-api-id, skipping")
-}
-
-type MockSessionHandler struct{}
-
-func (MockSessionHandler) Init(storage.Handler) {
-}
-
-func (MockSessionHandler) Store() storage.Handler {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) UpdateSession(string, *user.SessionState, int64, bool) error {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) RemoveSession(string, string, bool) bool {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) SessionDetail(string, string, bool) (user.SessionState, bool) {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) KeyExpired(*user.SessionState) bool {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) Sessions(string) []string {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) ResetQuota(string, *user.SessionState, bool) {
-	//TODO implement me
-	panic("implement me")
-}
-
-func (MockSessionHandler) Stop() {
-	//TODO implement me
-	panic("implement me")
-}
-
-type MockHealthChecker struct{}
-
-func (MockHealthChecker) Init(storage.Handler) {
-}
-
-func (MockHealthChecker) ApiHealthValues() (HealthCheckValues, error) {
-	//TODO implement me
-	panic("implement me")
-}
 
-func (MockHealthChecker) StoreCounterVal(HealthPrefix, string) {
-	//TODO implement me
-	panic("implement me")
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := recoverFromLoadApiPanic(tt.spec, tt.err)
+			if err == nil {
+				t.Fatal("expected error, got nil")
+			}
+			if !strings.Contains(err.Error(), tt.expected) {
+				t.Errorf("expected error to contain %q, got %q", tt.expected, err.Error())
+			}
+		})
+	}
 }