Join Preload panics

[emilienkofman]

GORM Playground Link

go-gorm/playground#735

Description

When using Join and Preload together, if we get more than 20 entries in the database it will panic (I guess due to this beeing 20)

gorm version 1.25.10

obtained stack trace:

Error Trace:	/home/emilien/Workspace/src/github.com/emilienkofman/playground/main_test.go:34
        	Error:      	func (assert.PanicTestFunc)(0xc9e8a0) should not panic
        	            		Panic value:	reflect: slice length out of range in SetLen
        	            		Panic stack:	goroutine 24 [running]:
        	            	runtime/debug.Stack()
        	            		/home/emilien/Workspace/go/src/runtime/debug/stack.go:24 +0x6b
        	            	github.com/stretchr/testify/assert.didPanic.func1()
        	            		/home/emilien/go/pkg/mod/github.com/stretchr/testify@v1.8.1/assert/assertions.go:1050 +0x73
        	            	panic({0xdf8380?, 0xf6ffd0?})
        	            		/home/emilien/Workspace/go/src/runtime/panic.go:770 +0x136
        	            	reflect.Value.SetLen({0xc0003fb100, 0xc00044f068, 0x197}, 0x15)
        	            		/home/emilien/Workspace/go/src/reflect/value.go:2423 +0x85
        	            	gorm.io/gorm/callbacks.preloadEntryPoint(0xc000488c00, {0xc0003dfeb0, 0x1, 0x1}, 0xc000444a28, 0xc000488660, {0x0, 0x0, 0x0})
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/gorm/callbacks/preload.go:128 +0x745
        	            	gorm.io/gorm/callbacks.Preload(0xc000488600)
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/gorm/callbacks/query.go:283 +0x4f7
        	            	gorm.io/gorm.(*processor).Execute(0xc0003feaf0, 0xc000488600)
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/gorm/callbacks.go:130 +0x67c
        	            	gorm.io/gorm.(*DB).Find(0xc000488600, {0xde9280, 0xc00044e258}, {0x0, 0x0, 0x0})
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/gorm/finisher_api.go:170 +0x285
        	            	gorm.io/playground.TestGORM.func1()
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/main_test.go:38 +0xac
        	            	github.com/stretchr/testify/assert.didPanic(0xc0003de590)
        	            		/home/emilien/go/pkg/mod/github.com/stretchr/testify@v1.8.1/assert/assertions.go:1055 +0x119
        	            	github.com/stretchr/testify/assert.NotPanics({0xf71740, 0xc0000f51e0}, 0xc0003de590, {0x0, 0x0, 0x0})
        	            		/home/emilien/go/pkg/mod/github.com/stretchr/testify@v1.8.1/assert/assertions.go:1126 +0x12c
        	            	gorm.io/playground.TestGORM(0xc0000f51e0)
        	            		/home/emilien/Workspace/src/github.com/emilienkofman/playground/main_test.go:34 +0x459
        	            	testing.tRunner(0xc0000f51e0, 0xf26bb0)
        	            		/home/emilien/Workspace/go/src/testing/testing.go:1689 +0x1da
        	            	created by testing.(*T).Run in goroutine 1
        	            		/home/emilien/Workspace/go/src/testing/testing.go:1742 +0x7d3

the test case is inspired with #6715 and likely related to the fix of that previous issue (but I've not been investigating enough)

#6715

[emilienkofman]

looks like this was introduced in 85299bf

@a631807682 do you have any insight on how to fix that? Let me know if I can help. I'm not sure exactly what to do at the moment.

[a631807682]

looks like this was introduced in 85299bf

@a631807682 do you have any insight on how to fix that? Let me know if I can help. I'm not sure exactly what to do at the moment.

Cap and Len are not handled correctly here, we need to handle them correctly, or avoid them through Append. Are you interested to create a PR for it?