Refactor request context (#32956)

Introduce RequestContext: is a short-lived context that is used to store
request-specific data.

RequestContext could be used to clean form tmp files, close context git
repo, and do some tracing in the future.

Then a lot of legacy code could be removed or improved. For example:
most `ctx.Repo.GitRepo.Close()` could be removed because the git repo
could be closed when the request is done.

modules/web/handler.go

@@ -4,7 +4,6 @@
 package web
 
 import (
-	goctx "context"
 	"fmt"
 	"net/http"
 	"reflect"
@@ -51,7 +50,6 @@ func (r *responseWriter) WriteHeader(statusCode int) {
 var (
 	httpReqType    = reflect.TypeOf((*http.Request)(nil))
 	respWriterType = reflect.TypeOf((*http.ResponseWriter)(nil)).Elem()
-	cancelFuncType = reflect.TypeOf((*goctx.CancelFunc)(nil)).Elem()
 )
 
 // preCheckHandler checks whether the handler is valid, developers could get first-time feedback, all mistakes could be found at startup
@@ -65,11 +63,8 @@ func preCheckHandler(fn reflect.Value, argsIn []reflect.Value) {
 	if !hasStatusProvider {
 		panic(fmt.Sprintf("handler should have at least one ResponseStatusProvider argument, but got %s", fn.Type()))
 	}
-	if fn.Type().NumOut() != 0 && fn.Type().NumIn() != 1 {
-		panic(fmt.Sprintf("handler should have no return value or only one argument, but got %s", fn.Type()))
-	}
-	if fn.Type().NumOut() == 1 && fn.Type().Out(0) != cancelFuncType {
-		panic(fmt.Sprintf("handler should return a cancel function, but got %s", fn.Type()))
+	if fn.Type().NumOut() != 0 {
+		panic(fmt.Sprintf("handler should have no return value other than registered ones, but got %s", fn.Type()))
 	}
 }
 
@@ -105,16 +100,10 @@ func prepareHandleArgsIn(resp http.ResponseWriter, req *http.Request, fn reflect
 	return argsIn
 }
 
-func handleResponse(fn reflect.Value, ret []reflect.Value) goctx.CancelFunc {
-	if len(ret) == 1 {
-		if cancelFunc, ok := ret[0].Interface().(goctx.CancelFunc); ok {
-			return cancelFunc
-		}
-		panic(fmt.Sprintf("unsupported return type: %s", ret[0].Type()))
-	} else if len(ret) > 1 {
+func handleResponse(fn reflect.Value, ret []reflect.Value) {
+	if len(ret) != 0 {
 		panic(fmt.Sprintf("unsupported return values: %s", fn.Type()))
 	}
-	return nil
 }
 
 func hasResponseBeenWritten(argsIn []reflect.Value) bool {
@@ -171,11 +160,8 @@ func toHandlerProvider(handler any) func(next http.Handler) http.Handler {
 			routing.UpdateFuncInfo(req.Context(), funcInfo)
 			ret := fn.Call(argsIn)
 
-			// handle the return value, and defer the cancel function if there is one
-			cancelFunc := handleResponse(fn, ret)
-			if cancelFunc != nil {
-				defer cancelFunc()
-			}
+			// handle the return value (no-op at the moment)
+			handleResponse(fn, ret)
 
 			// if the response has not been written, call the next handler
 			if next != nil && !hasResponseBeenWritten(argsIn) {

modules/web/middleware/data.go

@@ -7,46 +7,21 @@ import (
 	"context"
 	"time"
 
+	"code.gitea.io/gitea/modules/reqctx"
 	"code.gitea.io/gitea/modules/setting"
 )
 
-// ContextDataStore represents a data store
-type ContextDataStore interface {
-	GetData() ContextData
-}
-
-type ContextData map[string]any
-
-func (ds ContextData) GetData() ContextData {
-	return ds
-}
-
-func (ds ContextData) MergeFrom(other ContextData) ContextData {
-	for k, v := range other {
-		ds[k] = v
-	}
-	return ds
-}
-
 const ContextDataKeySignedUser = "SignedUser"
 
-type contextDataKeyType struct{}
-
-var contextDataKey contextDataKeyType
-
-func WithContextData(c context.Context) context.Context {
-	return context.WithValue(c, contextDataKey, make(ContextData, 10))
-}
-
-func GetContextData(c context.Context) ContextData {
-	if ds, ok := c.Value(contextDataKey).(ContextData); ok {
-		return ds
+func GetContextData(c context.Context) reqctx.ContextData {
+	if rc := reqctx.GetRequestDataStore(c); rc != nil {
+		return rc.GetData()
 	}
 	return nil
 }
 
-func CommonTemplateContextData() ContextData {
-	return ContextData{
+func CommonTemplateContextData() reqctx.ContextData {
+	return reqctx.ContextData{
 		"IsLandingPageOrganizations": setting.LandingPageURL == setting.LandingPageOrganizations,
 
 		"ShowRegistrationButton":        setting.Service.ShowRegistrationButton,

modules/web/middleware/flash.go

@@ -7,11 +7,13 @@ import (
 	"fmt"
 	"html/template"
 	"net/url"
+
+	"code.gitea.io/gitea/modules/reqctx"
 )
 
 // Flash represents a one time data transfer between two requests.
 type Flash struct {
-	DataStore ContextDataStore
+	DataStore reqctx.RequestDataStore
 	url.Values
 	ErrorMsg, WarningMsg, InfoMsg, SuccessMsg string
 }

modules/web/route.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/modules/htmlutil"
+	"code.gitea.io/gitea/modules/reqctx"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/web/middleware"
 
@@ -29,12 +30,12 @@ func Bind[T any](_ T) http.HandlerFunc {
 }
 
 // SetForm set the form object
-func SetForm(dataStore middleware.ContextDataStore, obj any) {
+func SetForm(dataStore reqctx.ContextDataProvider, obj any) {
 	dataStore.GetData()["__form"] = obj
 }
 
 // GetForm returns the validate form information
-func GetForm(dataStore middleware.ContextDataStore) any {
+func GetForm(dataStore reqctx.RequestDataStore) any {
 	return dataStore.GetData()["__form"]
 }