`Try It Out!` requests fail if `servers: []`

Q	A
Bug or feature request?	Bug
Which Swagger/OpenAPI version?	3.0.0
Which Swagger-UI version?	3.14.0 / g1f0dc054
How did you install Swagger-UI?	git
Which browser & version?	Chrome 66.0.3359.139 (Official Build) (64-bit)
Which operating system?	Ubuntu 18.04

Demonstration API definition

https://gist.githubusercontent.com/dtkav/c49eeb14bcf5bd2370f74ba79cce9358/raw/21ac1f4a18813e7cde2da51596d1a91fd86233a1/petstore.yml

openapi: 3.0.0
servers: []  # this breaks swagger-ui
# ... 
# for entire spec see gist linked above

Configuration (browser query string, constructor, config.yaml)

{
        url: "https://gist.githubusercontent.com/dtkav/c49eeb14bcf5bd2370f74ba79cce9358/raw/21ac1f4a18813e7cde2da51596d1a91fd86233a1/petstore.yml",
        dom_id: '#swagger-ui',
        deepLinking: true,
        presets: [
          SwaggerUIBundle.presets.apis,
          SwaggerUIStandalonePreset
        ],
        plugins: [
          SwaggerUIBundle.plugins.DownloadUrl
        ],
        layout: "StandaloneLayout"
      }

Expected Behavior

According to: https://swagger.io/docs/specification/api-host-and-base-path/ If the server block doesn’t exist, or is empty then it shall default to ‘/’ This seems to work for a missing servers block, but not for an empty list.

Current Behavior

and empty server block results in the following console error when attempting to make any requests:

system.js:461 TypeError: Cannot read property 'url' of undefined
    at s (index.js:1)
    at a (index.js:1)
    at Object.o [as buildRequest] (index.js:1)
    at actions.js:357
    at Object.dispatch (utils.js:121)
    at dispatch (<anonymous>:1:27776)
    at bindActionCreators.js:3
    at wrap-actions.js:30
    at Object.r (system.js:173)
    at Object.executeRequest (system.js:458)
    at actions.js:397
    at Object.dispatch (utils.js:121)
    at dispatch (<anonymous>:1:27776)
    at bindActionCreators.js:3
    at spec-wrap-actions.js:9
    at Object.r (system.js:173)
    at Object.execute (system.js:458)
    at r.onClick (execute.jsx:24)
    at Object.r (ReactErrorUtils.js:24)
    at a (EventPluginUtils.js:83)
    at Object.s [as executeDispatchesInOrder] (EventPluginUtils.js:106)
    at h (EventPluginHub.js:41)
    at m (EventPluginHub.js:52)
    at Array.forEach (<anonymous>)
    at r (forEachAccumulated.js:22)
    at Object.processEventQueue (EventPluginHub.js:252)
    at r (ReactEventEmitterMixin.js:15)
    at Object.handleTopLevel [as _handleTopLevel] (ReactEventEmitterMixin.js:25)
    at o (ReactEventListener.js:70)
    at r.perform (Transaction.js:141)
    at Object.batchedUpdates (ReactDefaultBatchingStrategy.js:60)
    at Object.o [as batchedUpdates] (ReactUpdates.js:95)
    at dispatchEvent (ReactEventListener.js:145)

Possible Solution

Looks like a default is set wrong, but I haven’t yet been able to track it down in the code.

Context

I converted an example petstore spec from swagger 2.0 to OAS3 using https://mermade.org.uk/openapi-converter and it output the following servers block.

servers: []

I then tried to use this with swagger UI and was unable to make any “Try It Out!” requests.

[dtkav]

ah ok TIL, thanks @shockey !

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