Wrong type detect for Example of a String field in YAML

[xlab]

Hello! I'm trying to generate API spec for a design like this:

package design

import (
	. "goa.design/goa/v3/dsl"
)

var _ = API("APITest", func() {

})

var _ = Service("ServiceTest", func() {
	Method("Main", func() {
		Payload(func() {
			Attribute("field1", String, func() {
				Example("0xffff")
			})
			Attribute("field2", String, func() {
				Example(`"0xffff"`)
			})
			Attribute("field3", String, func() {
				Example("0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498")
			})
			Attribute("field4", String, func() {
				Example(`"0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498"`)
			})
		})

		HTTP(func() {
			GET("/")
		})
	})
})

The problem is that the generated Swagger spec looks like this:

  ServiceTestMainRequestBody:
    title: ServiceTestMainRequestBody
    type: object
    properties:
      field1:
        type: string
        example: "0xffff"
      field2:
        type: string
        example: '"0xffff"'
      field3:
        type: string
        example: 0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498
      field4:
        type: string
        example: '"0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498"'
    example:
      field1: "0xffff"
      field2: '"0xffff"'
      field3: 0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498
      field4: '"0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498"'

As you can see, for some reason field3 is treated as a number! Which will affect the generated documentation later. And for some reason field1 is treated correctly.

So that's clearly a bug, I'm not sure why Goa tries to dynamically detect type if it is declared as String already in the spec. @raphael I need your help at this point :)

[xlab]

Clarification: the bug is somewhere near YAML generation, because JSON looks ok:

   "definitions": {
        "ServiceTestMainRequestBody": {
            "title": "ServiceTestMainRequestBody",
            "type": "object",
            "properties": {
                "field1": {
                    "type": "string",
                    "example": "0xffff"
                },
                "field2": {
                    "type": "string",
                    "example": "\"0xffff\""
                },
                "field3": {
                    "type": "string",
                    "example": "0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498"
                },
                "field4": {
                    "type": "string",
                    "example": "\"0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498\""
                }
            },
            "example": {
                "field1": "0xffff",
                "field2": "\"0xffff\"",
                "field3": "0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498",
                "field4": "\"0xf47261b0000000000000000000000000e41d2489571d322189246dafa5ebde1f4699f498\""
            }
        }
    }

[raphael]

Thank you for the report! Goa does not do any type inference. This looks like some weirdness in the YAML package that Goa uses (or Goa not using it correctly).

[saniales]

@raphael actually since YAML accepts strings only, we can actually put the "" under every field and solving this issue, what do you think?

[raphael]

@saniales if that works then sounds good! I believe the issue is that sometimes the YAML package will add these quotes and sometimes it won't which means that if we always add them it might double escape them?

[xlab]

@saniales

actually since YAML accepts strings only

Well not only strings - YAML natively encodes scalars (such as strings, integers, and floats)

[saniales]

@raphael @xlab what we actually care is not to be pure about yaml types, instead that they are shown correctly in openapi spec, being string the type we can stringify everything and it should work

[xlab]

@saniales I agree, that might be the approach

[raphael]

@saniales give it a shot, I suspect that the result is going to be that they are all strings but that "sometimes" the string will be quoted which may or may not be an issue for OpenAPI spec examples.

[saniales]

will give it a shot in the coming days

[saniales]

I confirm that this can be solved by using single quotes only with string values

And I also confirm that JSON generated openapi is not affected by this, only YAML

[raphael]

Would you care to make a PR that adds the quote?