utils/checkpackagelib: warn about ifdef on .mk

There are two legitimate cases to prefer ifdef over ifeq in package
recipes: command-line overrides are allowed for busybox and uclibc
configs.

Except for that, all package in tree already use ifeq, so warn the
developer adding/changing a package to use ifeq instead of ifdef, in
order to keep consistence across packages.
file.mk:2: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL
file.mk:5: use ifneq ($(SYMBOL),y) instead of ifndef SYMBOL

The difference between ifeq and ifdef is that ifdef doesn't expand
recursively.

Add comments to busybox and uclibc packages to avoid a warning in such
special cases.

Cc: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/busybox/busybox.mk

@@ -110,6 +110,7 @@ BUSYBOX_MAKE_OPTS = \
 
 # specifying BUSYBOX_CONFIG_FILE on the command-line overrides the .config
 # setting.
+# check-package disable Ifdef
 ifndef BUSYBOX_CONFIG_FILE
 BUSYBOX_CONFIG_FILE = $(call qstrip,$(BR2_PACKAGE_BUSYBOX_CONFIG))
 endif

package/uclibc/uclibc.mk

@@ -22,6 +22,7 @@ UCLIBC_DEPENDENCIES = host-gcc-initial linux-headers
 
 # specifying UCLIBC_CONFIG_FILE on the command-line overrides the .config
 # setting.
+# check-package disable Ifdef
 ifndef UCLIBC_CONFIG_FILE
 UCLIBC_CONFIG_FILE = $(call qstrip,$(BR2_UCLIBC_CONFIG))
 endif

utils/checkpackagelib/lib_mk.py

@@ -21,6 +21,24 @@ continue_conditional = ["elif", "else"]
 end_conditional = ["endif"]
 
 
+class Ifdef(_CheckFunction):
+    IFDEF = re.compile(r"^\s*(else\s+|)(ifdef|ifndef)\s")
+
+    def check_line(self, lineno, text):
+        m = self.IFDEF.search(text)
+        if m is None:
+            return
+        word = m.group(2)
+        if word == 'ifdef':
+            return ["{}:{}: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL"
+                    .format(self.filename, lineno),
+                    text]
+        else:
+            return ["{}:{}: use ifneq ($(SYMBOL),y) instead of ifndef SYMBOL"
+                    .format(self.filename, lineno),
+                    text]
+
+
 class Indent(_CheckFunction):
     COMMENT = re.compile(r"^\s*#")
     CONDITIONAL = re.compile(r"^\s*({})\s".format("|".join(start_conditional + end_conditional + continue_conditional)))

utils/checkpackagelib/test_lib_mk.py

@@ -3,6 +3,54 @@ import checkpackagelib.test_util as util
 import checkpackagelib.lib_mk as m
 
 
+Ifdef = [
+    ('ignore commented line',
+     'any',
+     '# ifdef\n',
+     []),
+    ('simple',
+     'any',
+     '\n'
+     'ifdef BR2_PACKAGE_FWTS_EFI_RUNTIME_MODULE\n'
+     'endif\n',
+     [['any:2: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL',
+       'ifdef BR2_PACKAGE_FWTS_EFI_RUNTIME_MODULE\n']]),
+    ('ignore indentation',
+     'any',
+     '  ifdef FOO\n'
+     '  endif\n'
+     '\tifdef BAR\n'
+     'endif\n',
+     [['any:1: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL',
+       '  ifdef FOO\n'],
+      ['any:3: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL',
+       '\tifdef BAR\n']]),
+    ('typo',
+     'any',
+     '\n'
+     'ifndef ($(BR2_ENABLE_LOCALE),y)\n'
+     'endif\n',
+     [['any:2: use ifneq ($(SYMBOL),y) instead of ifndef SYMBOL',
+       'ifndef ($(BR2_ENABLE_LOCALE),y)\n']]),
+    ('else ifdef',
+     'any',
+     'else ifdef  SYMBOL # comment\n',
+     [['any:1: use ifeq ($(SYMBOL),y) instead of ifdef SYMBOL',
+       'else ifdef  SYMBOL # comment\n']]),
+    ('else ifndef',
+     'any',
+     '\t else  ifndef\t($(SYMBOL),y) # comment\n',
+     [['any:1: use ifneq ($(SYMBOL),y) instead of ifndef SYMBOL',
+       '\t else  ifndef\t($(SYMBOL),y) # comment\n']]),
+    ]
+
+
+@pytest.mark.parametrize('testname,filename,string,expected', Ifdef)
+def test_Ifdef(testname, filename, string, expected):
+    warnings = util.check_file(m.Ifdef, filename, string)
+    assert warnings == expected
+
+
 Indent = [
     ('ignore comment at beginning of line',
      'any',