Using ArrayOf in MediaType→Attributes→Attribute causes generator crash

[danderson]

I have a DSL that causes a nil pointer dereference crash when running goagen. This is not an ideal way of telling me I made a mistake :P. Minimal repro design:

package design

import (
	. "github.com/goadesign/goa/design"
	. "github.com/goadesign/goa/design/apidsl"
)

var _ = API("crash", func() {})

var _ = MediaType("thing", func() {
	Attributes(func() {
		Attribute("rec", ArrayOf("thing"))
	})

	View("default", func() {
		Attribute("rec")
	})
})

The error in this design is that I should have used CollectionOf, not ArrayOf.

Running goagen bootstrap on this design results in a nil pointer dereference crash:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4a37e2]

goroutine 1 [running]:
panic(0x795780, 0xc4200100e0)
	/usr/lib/go/src/runtime/panic.go:500 +0x1a1
github.com/goadesign/goa/design.(*UserTypeDefinition).IsPrimitive(0x0, 0xc420163670)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/types.go:642 +0x22
github.com/goadesign/goa/design.(*AttributeDefinition).Validate(0xc42018be80, 0xc420163680, 0xf, 0x9ebd60, 0xc42018bf00, 0xc420163670)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:451 +0x139
github.com/goadesign/goa/design.(*AttributeDefinition).Validate(0xc42018bf00, 0xc420163670, 0xc, 0x9ebfe0, 0xc420168e80, 0xc420163660)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:484 +0x982
github.com/goadesign/goa/design.(*AttributeDefinition).Validate(0xc42018bd80, 0x0, 0x0, 0x9ebfe0, 0xc420168e80, 0xc41fff4d49)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:479 +0x451
github.com/goadesign/goa/design.(*UserTypeDefinition).Validate(0xc420168e80, 0x0, 0x0, 0x9ebea0, 0xc42016f3c0, 0x40f69e)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:520 +0xa8
github.com/goadesign/goa/design.(*MediaTypeDefinition).Validate(0xc42016f3c0, 0x9f13a0)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:528 +0xa6
github.com/goadesign/goa/design.(*APIDefinition).Validate.func2(0xc42016f3c0, 0xc4201c6510, 0xc4201634c0)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:146 +0x49
github.com/goadesign/goa/design.(*APIDefinition).IterateMediaTypes(0xc4201922c0, 0xc42020f9d8, 0x0, 0x0)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/definitions.go:528 +0x1d8
github.com/goadesign/goa/design.(*APIDefinition).Validate(0xc4201922c0, 0x9ebce0, 0xc4201922c0)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/validation.go:148 +0x333
github.com/goadesign/goa/dslengine.validateSet(0xc420163610, 0x1, 0x1, 0xa2b908, 0x0)
	/home/dave/hack/go/src/github.com/goadesign/goa/dslengine/runner.go:312 +0x120
github.com/goadesign/goa/design.(*APIDefinition).IterateSets(0xc4201922c0, 0x84ca30)
	/home/dave/hack/go/src/github.com/goadesign/goa/design/definitions.go:458 +0x96
github.com/goadesign/goa/dslengine.Run(0x9ed460, 0xc420168ea0)
	/home/dave/hack/go/src/github.com/goadesign/goa/dslengine/runner.go:108 +0x197
main.main()
	/home/dave/hack/go/src/go.universe.tf/gipam/goagen171272070/main.go:24 +0x63

[raphael]

Thanks for the report. It's actually legal to use ArrayOf on a media type - unusual but legal. The difference between CollectionOf and ArrayOf is in what they produce (media type vs. user type) - not in what they accept as parameter.