Support disabling warnings for redundant assignments

The Linux Kernel's merge_config.sh defaults to disabling warnings for
redundant assignments and has support for enabling them
specifically. This patch reproduces this behaviour in kconfiglib
except that we retaing kconfiglib's default behaviour of enabling the
warnings.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>

1 files changed, 31 insertions, 4 deletions

diff --git a/kconfiglib.py b/kconfiglib.py
index 261dc93..d91c27c 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -486,6 +486,7 @@ class Kconfig(object):
     __slots__ = (
         "_choices",
         "_print_undef_assign",
+        "_print_redun_assign",
         "_print_warnings",
         "_set_re_match",
         "_unset_re_match",
@@ -561,6 +562,7 @@ class Kconfig(object):
 
         self._print_warnings = warn
         self._print_undef_assign = False
+        self._print_redun_assign = True
 
         self.syms = {}
         self.const_syms = {}
@@ -808,10 +810,14 @@ class Kconfig(object):
                         display_val = val
                         display_user_val = sym.user_value
 
-                    self._warn('{} set more than once. Old value: "{}", new '
-                               'value: "{}".'
-                               .format(name, display_user_val, display_val),
-                               filename, linenr)
+                    warn_msg = '{} set more than once. Old value: "{}", new value: "{}".'.format(
+                        name, display_user_val, display_val
+                    )
+
+                    if display_user_val == display_val:
+                        self._warn_redun_assign(warn_msg, filename, linenr)
+                    else:
+                        self._warn(             warn_msg, filename, linenr)
 
                 sym.set_value(val)
 
@@ -1032,6 +1038,19 @@ class Kconfig(object):
         """
         self._print_undef_assign = False
 
+    def enable_redun_warnings(self):
+        """
+        Enables warnings for redundant assignments to symbols. Printed to
+        stderr. Enabled by default.
+        """
+        self._print_redun_assign = True
+
+    def disable_redun_warnings(self):
+        """
+        See enable_redun_warnings().
+        """
+        self._print_redun_assign = False
+
     def __repr__(self):
         """
         Returns a string with information about the Kconfig object when it is
@@ -1046,6 +1065,8 @@ class Kconfig(object):
             "warnings " + ("enabled" if self._print_warnings else "disabled"),
             "undef. symbol assignment warnings " +
                 ("enabled" if self._print_undef_assign else "disabled"),
+            "redundant symbol assignment warnings " +
+                ("enabled" if self._print_redun_assign else "disabled")
         )))
 
     #
@@ -2122,6 +2143,12 @@ class Kconfig(object):
             'attempt to assign the value "{}" to the undefined symbol {}' \
             .format(val, name), filename, linenr)
 
+    def _warn_redun_assign(self, msg, filename=None, linenr=None):
+        """
+        See the class documentation.
+        """
+        if self._print_redun_assign:
+            _stderr_msg("warning: " + msg, filename, linenr)
 
 class Symbol(object):
     """