feat(rendering): gate rendering based on valid version identifiers (#4614)

* create VersionPragmaFilter component

* use VersionPragmaFilter in BaseLayout

* tighten version idenitifier constraints

* handle case where user specifies a valid `swagger` and `openapi` field

* add traceable class names for each message

* add tests

* linter fixes!

* UNRELATED CHANGE: remove travis short-circuit

* add bypass switch to VersionPragmaFilter

test/components/version-pragma-filter.js

@@ -0,0 +1,70 @@
+/* eslint-env mocha */
+import React from "react"
+import expect, { createSpy } from "expect"
+import { shallow } from "enzyme"
+import { fromJS, Map } from "immutable"
+import VersionPragmaFilter from "components/version-pragma-filter"
+
+describe("<VersionPragmaFilter/>", function(){
+  it("renders children for a Swagger 2 definition", function(){
+    // When
+    let wrapper = shallow(
+      <VersionPragmaFilter isSwagger2={true} isOAS3={false}>
+        hello!
+      </VersionPragmaFilter>
+    )
+
+    // Then
+    expect(wrapper.find("div").length).toEqual(1)
+    expect(wrapper.find("div").text()).toEqual("hello!")
+  })
+  it("renders children for an OpenAPI 3 definition", function(){
+    // When
+    let wrapper = shallow(
+      <VersionPragmaFilter isSwagger2={false} isOAS3={true}>
+        hello!
+      </VersionPragmaFilter>
+    )
+
+    // Then
+    expect(wrapper.find("div").length).toEqual(1)
+    expect(wrapper.find("div").text()).toEqual("hello!")
+  })
+  it("renders children when a bypass prop is set", function(){
+    // When
+    let wrapper = shallow(
+      <VersionPragmaFilter bypass>
+        hello!
+      </VersionPragmaFilter>
+    )
+
+    // Then
+    expect(wrapper.find("div").length).toEqual(1)
+    expect(wrapper.find("div").text()).toEqual("hello!")
+  })
+  it("renders the correct message for an ambiguous-version definition", function(){
+    // When
+    let wrapper = shallow(
+      <VersionPragmaFilter isSwagger2={true} isOAS3={true}>
+        hello!
+      </VersionPragmaFilter>
+    )
+
+    // Then
+    expect(wrapper.find("div.version-pragma__message--ambiguous").length).toEqual(1)
+    expect(wrapper.find("div.version-pragma__message--missing").length).toEqual(0)
+  })
+  it("renders the correct message for a missing-version definition", function(){
+    // When
+    let wrapper = shallow(
+      <VersionPragmaFilter isSwagger2={false} isOAS3={false}>
+        hello!
+      </VersionPragmaFilter>
+    )
+
+    // Then
+    expect(wrapper.find("div.version-pragma__message--missing").length).toEqual(1)
+    expect(wrapper.find("div.version-pragma__message--ambiguous").length).toEqual(0)
+  })
+
+})