According to https://www.yoctoproject.org/docs/1.6/bitbake-user-manual/bitbake-user-manual.html#shell-functions I can call other shell functions

However this did not work

do_install_prepend_jetson-nano-emmc() {
        install -d ${D}/etc
        install -d ${D}/etc/network
        install -m 0640 ${WORKDIR}/interfaces_nano ${D}/etc/network/interfaces
}

do_install_prepend_jetson-nano-devkit-emmc() {
        do_install_prepend_jetson-nano-emmc
}

Idea here was to use the same code for two different machines

The dump dumps all the environment. In the beginning it says

Traceback (most recent call last):
  File "/workdir/poky/bitbake/lib/bb/siggen.py", line 150, in SignatureGeneratorOEEquivHash._build_data(fn='/workdir/layers/myrecipe.bb', d=<bb.data_smart.DataSmart object at 0x7fd122baf6a0>):
             ignore_mismatch = ((d.getVar("BB_HASH_IGNORE_MISMATCH") or '') == '1')
    >        tasklist, gendeps, lookupcache = bb.data.generate_dependencies(d, self.basewhitelist)

Then there is the env; at the end there is:

                     parser = bb.codeparser.ShellParser(key, logger)
    >                parser.parse_shell(parsedvar.value)
                     deps = deps | shelldeps
  File "/workdir/poky/bitbake/lib/bb/codeparser.py", line 343, in ShellParser.parse_shell(value=None):

    >        self._parse_shell(value)
             self.execs = set(cmd for cmd in self.allexecs if cmd not in self.funcdefs)
  File "/workdir/poky/bitbake/lib/bb/codeparser.py", line 354, in ShellParser._parse_shell(value=None):
             except Exception:
    >            bb.error('Error during parse shell code, the last 5 lines are:\n%s' % '\n'.join(value.split('\n')[-5:]))
                 raise
AttributeError: 'NoneType' object has no attribute 'split'


I've no idea is this is an issue in bitbake or in the documentation or in poky
(btw this is on dunfell)