Spring NullPointerException in MockHttpServletRequestBuilder for URI string with no protocol

Affects: spring-boot-starter-test 2.1.6.RELEASE

Use Case: When performing an spring integration test over a get controller we add an url as a String to MockHttpServletRequestBuilder to perform such action.

Issue: When we add that url String without the protocol (for instance: "localhost:port...") the request returns a NullPointerException.

Code failing:

MockHttpServletResponse response = 
    mockMvc.perform(MockMvcRequestBuilders.get("localhost:port/some domain/etc...")).andReturn().getResponse();

Code working:

MockHttpServletResponse response = 
    mockMvc.perform(MockMvcRequestBuilders.get("http://localhost:port/some domain/etc...")).andReturn().getResponse();

Just to clarify the only difference is that the second url contains the http protcol explicitly declared

Expectation: Since http is the default protocol in many other frameworks I expect it to be inferred as url protocl if no other is defined explicitly.

Cause: Inside that MockMvcRequestBuilders.get("uri") method there is a call to a private constructor who converts that String into an actual URI

MockHttpServletRequestBuilder(HttpMethod httpMethod, String url, Object... vars) {
    this(httpMethod.name(), UriComponentsBuilder.fromUriString(url).buildAndExpand(vars).encode().toUri());
}

But it does not work properly since this.utl.getRawPath() returns null which later causes updatePathRequestProperties to throw mentioned NullPointerException

Thanks in advance!

Comment From: rstoyanchev

MockMvcRequestBuilders uses UriComponentsBuilder.fromUriString, which can't parse the given input correctly because "localhost:" looks like a scheme.

Switching to UriComponentsBuilder.fromHttpUrl provides a more helpful error:

java.lang.IllegalArgumentException: [localhost:8080/path] is not a valid HTTP URL

I don't we should go further and fill in the protocol since we don't know if that should be "http:" or "https:" and that could lead to surprises, and possibly even possible contradictions (e.g. "localhost:443").

Comment From: rstoyanchev

Actually it looks like fromUriString is quite useful because it allows to provide a path only. We need to keep that so it comes down to, either provide a URI with a path only (i.e. no scheme, host, port), or otherwise a proper HTTP URL.

If you want shorter, why not skip the host and port too?