fix: path-item $ref produces/consumes inheritance (via #5049)

* implement a selector for consumes options

* fix incorrect comment, test names

* add `consumesOptionsFor` selector

* use `consumesOptionsFor` and drop `operationConsumes`

src/core/plugins/spec/selectors.js

@@ -401,12 +401,6 @@ export function contentTypeValues(state, pathMethod) {
   })
 }
 
-// Get the consumes/produces by path
-export function operationConsumes(state, pathMethod) {
-  pathMethod = pathMethod || []
-  return specJsonWithResolvedSubtrees(state).getIn(["paths", ...pathMethod, "consumes"], fromJS({}))
-}
-
 // Get the currently selected produces value for an operation
 export function currentProducesFor(state, pathMethod) {
   pathMethod = pathMethod || []
@@ -425,6 +419,48 @@ export function currentProducesFor(state, pathMethod) {
 
 }
 
+// Get the produces options for an operation
+export function producesOptionsFor(state, pathMethod) {
+  pathMethod = pathMethod || []
+
+  const spec = specJsonWithResolvedSubtrees(state)
+  const operation = spec.getIn([ "paths", ...pathMethod], null)
+
+  if(operation === null) {
+    // return nothing if the operation does not exist
+    return
+  }
+
+  const [path] = pathMethod
+
+  const operationProduces = operation.get("produces", null)
+  const pathItemProduces = spec.getIn(["paths", path, "produces"], null)
+  const globalProduces = spec.getIn(["produces"], null)
+
+  return operationProduces || pathItemProduces || globalProduces
+}
+
+// Get the consumes options for an operation
+export function consumesOptionsFor(state, pathMethod) {
+  pathMethod = pathMethod || []
+
+  const spec = specJsonWithResolvedSubtrees(state)
+  const operation = spec.getIn(["paths", ...pathMethod], null)
+
+  if (operation === null) {
+    // return nothing if the operation does not exist
+    return
+  }
+
+  const [path] = pathMethod
+
+  const operationConsumes = operation.get("consumes", null)
+  const pathItemConsumes = spec.getIn(["paths", path, "consumes"], null)
+  const globalConsumes = spec.getIn(["consumes"], null)
+
+  return operationConsumes || pathItemConsumes || globalConsumes
+}
+
 export const operationScheme = ( state, path, method ) => {
   let url = state.get("url")
   let matchResult = url.match(/^([a-z][a-z0-9+\-.]*):/)