The dev server now checks if path matches a file

[KyleAMathews]

Previously it'd return HTML if the accept header had text/html in it
which when a browser requests an unknown file, it always does.

This caused trouble when someone developing a site would try to click on
a link to a static file and instead of the dev server then returning
that file, it'd return an html file.

Fixes #255

[KyleAMathews]

@benstepp I started down the path for testing this but ran into roadblock where needed to start dev server but... got stuck after trying for a while... if you want to take a crack at testing this that'd be appreciated. My test plan was 1) start dev server 2) request (using ava-http) a markdown file directly & its page equivalent and then assert that we got what was expected in each.

[benstepp]

I should be able to take a real stab at this this weekend. I set this up and it works, but I'm not happy with the code duplication. Might be better and faster to test the Hapi server directly rather than booting up the CLI.

Some of the challenges with testing the development server

• the asynchronous nature of ava and multiple processes wanting to bind to the same port. I just dunked a test.serial here, but there is most definitely a better solution.
• how to tell when the server is actually ready to serve requests. Reading the stdout is probably not the answer either.

//support.js
export function develop (fixturePath) {
  const child = spawnNative(babel, ['--', gatsbyCli, 'develop'], { cwd: fixturePath })
  let stdout
  let stderr

  const ready = new Promise((resolve, reject) => {
    child.stderr.on('data', data => { stderr += data })
    child.stdout.on('data', data => {
      stdout += data
      if (includes(stdout, 'webpack building') &&
          includes(data.toString(), 'webpack built')) {
        resolve(true)
      }
    })

    child.on('error', error => reject({ error, stderr, stdout }))
    child.on('exit', code => {
      if (code === 0) {
        resolve({ code, stdout, stderr })
      } else {
        reject({ code, stdout, stderr })
      }
    })
  })

  return {
    start (t) {
      setTimeout(() => {
        t.end()
        child.kill()
      }, 10000)
      return ready
    },
    kill () {
      child.kill()
    },
  }
}

//in a test
test.serial('has a bundle', async t => {
  const server = develop(fixturePath)
  await server.start(t)
  const response = await http.getResponse('http://0.0.0.0:8000/bundle.js')
  t.is(response.statusCode, 200)
  server.kill()
})

[KyleAMathews]

Oh this looks great!

Waiting for the Webpack "ok" text is a bit fragile but I can't think of any other way off-hand to know if it's working. And as long as Webpack doesn't change the text we're good.

On the port issue — something like this could work https://www.npmjs.com/package/find-open-port