What is the correct format for Firefox build `--with-bing-api-keyfile`?

Question

I try to build firefox with specifying a bing API key (ac_add_options --with-bing-api-keyfile=</path/to/keyfile> in the .mozconfig). However, when configuration runs, I get the error ERROR: Bing API key file has an invalid format. I provided the API within the file </path/to/keyfile> as a string of 64 characters (with or without a trailing newline, both does not work).

Answer 1

The answer is:

The username to which the API key belongs needs to be prepended, separated by whitespace. So the format should be

<https://www.bingmapsportal.com/-Username> <API key>

Looking at the python script that checks the firefox-build-configuration suggests that there is some information like an ID needed:

[...]
      with MockedOpen({'key': 'fake-id fake-key\n'}):
        config, output, status = self.get_result(
            "id_and_secret_keyfile('Bing API')",
            args=['--with-bing-api-keyfile=key'],
            includes=includes)
        self.assertEqual(status, 0)
        self.assertEqual(output, textwrap.dedent('''\
            checking for the Bing API key... yes
        '''))
        self.assertEqual(config, {
            'MOZ_BING_API_CLIENTID': 'fake-id',
            'MOZ_BING_API_KEY': 'fake-key',
        })

    with MockedOpen({'key': 'fake-key\n'}):
        config, output, status = self.get_result(
            "id_and_secret_keyfile('Bing API')",
            args=['--with-bing-api-keyfile=key'],
            includes=includes)
        self.assertEqual(status, 1)
        self.assertEqual(output, textwrap.dedent('''\
            checking for the Bing API key... no
            ERROR: Bing API key file has an invalid format.
        '''))
        self.assertEqual(config, {})
[...]