bitbake conditional inclusion of depends statement

问题

How do I include a depends line in a bitbake file with a condition ? I want something like below:

if (some env varible)
  DEPENDS += "recipe-1"
else
  DEPENDS += "recipe-2'

I have tried below in the .bb file:

DEPENDS += "${@ 'recipe-2' if '${ENV_VAR}' else 'recipe-1'}"

Before that I exported ENV_VAR to BB_ENV_EXTRAWHITE

export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE ENV_VAR"

This is working only when ENV_VAR is set:

env ENV_VAR="value" bitbake test-recipe

if ENV_VAR is not set, it is throwing an error while parsing the bitbake DEPENDS line

ExpansionError: Failure expanding variable DEPENDS, expression was
${@ 'recipe-2' if '${ENV_VAR}' else 'recipe-1'}  
which triggered exception SyntaxError: EOL while scanning string literal (DEPENDS, line 1)

回答1:

Try:

DEPENDS += "${@ 'recipe-2' if d.getVar('ENV_VAR') else 'recipe-1'}"

The reason why is that ${ENV_VAR} gets expanded to the value of the variable. If its unset, it doesn't get expanded and that triggers the error you see. By using getVar you get a result which the rest of the python expression can deal with None or a value.

Note that there are some proposed changes which might improve the behaviour to make this a bit more usable and understandable to people but the above would continue to work regardless.

来源：https://stackoverflow.com/questions/35268512/bitbake-conditional-inclusion-of-depends-statement