check_compliance.py: Check for duplicated dependencies on Kconfig syms

Check for e.g. 'if FOO' within 'if FOO', or 'depends on FOO' within 'if
FOO'. Such duplicated dependencies make it easier to mess up changes to
Kconfig files (because it's not obvious that the same dependency is
added twice), and make the autogenerated documentation uglier.

Some of them might have been added due to Kconfig misunderstandings too.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

Author: ulfalizer

scripts/check_compliance.py

@@ -237,6 +237,7 @@ def run(self):
 
         self.check_top_menu_not_too_long(kconf)
         self.check_no_pointless_menuconfigs(kconf)
+        self.check_no_redundant_deps(kconf)
         self.check_no_undef_within_kconfig(kconf)
         self.check_no_undef_outside_kconfig(kconf)
 
@@ -361,6 +362,30 @@ def check_no_pointless_menuconfigs(self, kconf):
 """ + "\n".join(f"{node.item.name:35} {node.filename}:{node.linenr}"
                 for node in bad_mconfs))
 
+    def check_no_redundant_deps(self, kconf):
+        # Checks that there are no duplicated direct dependencies, e.g. a
+        # 'depends on FOO' on a symbol defined within an 'if FOO'. Redundant
+        # dependencies make changes harder to get right, and make the generated
+        # Kconfig documentation uglier.
+
+        # 'kconfiglib' is global
+        # pylint: disable=undefined-variable
+
+        for node in kconf.node_iter():
+            deps = kconfiglib.split_expr(node.dep, kconfiglib.AND)
+            for dep, count in collections.Counter(deps).items():
+                if count > 1:
+                    self.add_failure(f"""\
+Duplicated {kconfiglib.expr_str(dep)} dependency on symbol/choice/menu/comment
+at {node.filename}:{node.linenr}:
+
+{node}
+
+Jump to the item in the menuconfig/guiconfig interface (with '/') and check the
+'included via ...' path to figure out where the redundant dependency is coming
+from. You might have an 'if FOO' within an 'if FOO', or a 'depends on FOO'
+within an 'if FOO'.""")
+
     def check_no_undef_within_kconfig(self, kconf):
         """
         Checks that there are no references to undefined Kconfig symbols within