[PATCH] build/data: Don't expand python functions before execution [API change]

[Richard Purdie <richard.purdie@linuxfoundation.org>]

Right now, if you have some python code like:

X = "a"

def somefunction(d):
    d.setVar("X", "b")
    d.setVar("Y", "${X}")

then any sane person would expect that Y = "b" at the end of the
function. This is not the case, Y = "a".

This is due to the python function being expanded before execution, the
executed code would read d.setVar("Y", "a"). This understandably
confuses people, it also makes it near impossible to write ${} in a
python function without unintended things happening.

I think there is general agreement we should fix this and standardise
on non-expansion of python functions. We already don't expand anonymous
python (mostly).

I've checked OE-Core with buildhistory before and after this change and
there were a small number of issues this exposed which I've sent
patches for.

I propose we default to not expanding python code and then deal with
any consequences from that if/as/where identified. This will improve
new user understanding and usability of the system, it also allows
several long standing weird expansion issues to be fixed.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

diff --git a/bitbake/lib/bb/build.py b/bitbake/lib/bb/build.py
index 52a4916..b7c49eb 100644
--- a/bitbake/lib/bb/build.py
+++ b/bitbake/lib/bb/build.py
@@ -239,7 +239,7 @@ def exec_func_python(func, d, runfile, cwd=None):
     """Execute a python BB 'function'"""
 
     bbfile = d.getVar('FILE', True)
-    code = _functionfmt.format(function=func, body=d.getVar(func, True))
+    code = _functionfmt.format(function=func, body=d.getVar(func, False))
     bb.utils.mkdirhier(os.path.dirname(runfile))
     with open(runfile, 'w') as script:
         bb.data.emit_func_python(func, script, d)
diff --git a/bitbake/lib/bb/data.py b/bitbake/lib/bb/data.py
index 1f1f0d2..86ad4ed 100644
--- a/bitbake/lib/bb/data.py
+++ b/bitbake/lib/bb/data.py
@@ -308,7 +308,7 @@ def emit_func_python(func, o=sys.__stdout__, d = init()):
 
     write_func(func, o, True)
     pp = bb.codeparser.PythonParser(func, logger)
-    pp.parse_python(d.getVar(func, True))
+    pp.parse_python(d.getVar(func, False))
     newdeps = pp.execs
     newdeps |= set((d.getVarFlag(func, "vardeps", True) or "").split())
     seen = set()