Have load_config() and write_(min_)config() return messages

Hardcoding load_config() and write_(min_)config() to write any message
to stdout is awkward, because it means that the message can't be easily
reused when stdout is the wrong place to write it to (e.g. in
menuconfig/guiconfig). This gets extra bad now that there's also the "No
change to ..." message.

Modify load_config() and write_(min_)config() to return the message as a
string instead, and have them always return a message, instead of just
when 'filename' is None and verbose=True. This makes things flexible and
straightforward.

Use the new behavior in menuconfig.py and guiconfig.py. They now show
"No change to ..." when saving a file doesn't modify it.

Tools that want to write messages to stdout should now do
print(kconf.load_config()) / print(kconf.write_config()).

There's no clean way to preserve perfect backwards compatibility here,
but keep accepting the 'verbose' argument and print a deprecation
warning if a value is ever passed for it. That way, scripts will keep
running, though possibly with less output on stdout.

This changes the meaning of the load_config() return value as well,
though I suspect it was only ever used by the menuconfig/guiconfig
interfaces.

The new behavior applies for kconfiglib.VERSION >= (12, 0, 0).

alldefconfig.py

@@ -20,7 +20,7 @@
 def main():
     kconf = kconfiglib.standard_kconfig()
     kconfiglib.load_allconfig(kconf, "alldef.config")
-    kconf.write_config()
+    print(kconf.write_config())
 
 
 if __name__ == "__main__":

allmodconfig.py

@@ -39,7 +39,7 @@ def main():
 
     kconfiglib.load_allconfig(kconf, "allmod.config")
 
-    kconf.write_config()
+    print(kconf.write_config())
 
 
 if __name__ == "__main__":

allnoconfig.py

@@ -38,7 +38,7 @@ def main():
 
     kconfiglib.load_allconfig(kconf, "allno.config")
 
-    kconf.write_config()
+    print(kconf.write_config())
 
 
 if __name__ == "__main__":

allyesconfig.py

@@ -49,7 +49,7 @@ def main():
 
     kconfiglib.load_allconfig(kconf, "allyes.config")
 
-    kconf.write_config()
+    print(kconf.write_config())
 
 
 if __name__ == "__main__":

defconfig.py

@@ -35,8 +35,8 @@ def main():
     args = parser.parse_args()
 
     kconf = kconfiglib.Kconfig(args.kconfig)
-    kconf.load_config(args.config)
-    kconf.write_config()
+    print(kconf.load_config(args.config))
+    print(kconf.write_config())
 
 
 if __name__ == "__main__":

examples/allnoconfig_walk.py

@@ -63,4 +63,4 @@ def do_allnoconfig(node):
     if not changed:
         break
 
-kconf.write_config()
+print(kconf.write_config())

examples/defconfig_oldconfig.py

@@ -36,4 +36,4 @@
         s.set_value(0)
 
 # Write the final configuration
-kconf.write_config()
+print(kconf.write_config())

examples/menuconfig_example.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python
+
 # Implements a simple configuration interface on top of Kconfiglib to
 # demonstrate concepts for building a menuconfig-like. Emulates how the
 # standard menuconfig prints menu entries.
@@ -117,6 +119,7 @@
 #
 #   Enter a symbol/choice name, "load_config", or "write_config" (or press CTRL+D to exit): ^D
 
+from __future__ import print_function
 import readline
 import sys
 
@@ -300,27 +303,22 @@ def get_value_from_user(sc):
 
         if cmd == "load_config":
             config_filename = input(".config file to load: ")
-
             try:
-                kconf.load_config(config_filename)
+                # Returns a message telling which file got loaded
+                print(kconf.load_config(config_filename))
             except IOError as e:
-                # Print the (spammy) error from Kconfiglib itself
-                print(e.message + "\n")
-            else:
-                print("Configuration loaded from " + config_filename)
+                print(e, file=sys.stderr)
 
             print_menuconfig(kconf)
             continue
 
         if cmd == "write_config":
             config_filename = input("To this file: ")
-
             try:
-                kconf.write_config(config_filename)
+                # Returns a message telling which file got saved
+                print(kconf.write_config(config_filename))
             except IOError as e:
-                print(e.message)
-            else:
-                print("Configuration written to " + config_filename)
+                print(e, file=sys.stderr)
 
             continue
 
@@ -340,5 +338,5 @@ def get_value_from_user(sc):
 
             continue
 
-        print("No symbol/choice named '{}' in the configuration"
-              .format(cmd))
+        print("No symbol/choice named '{}' in the configuration".format(cmd),
+              file=sys.stderr)

examples/merge_config.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python
+
 # This script functions similarly to scripts/kconfig/merge_config.sh from the
 # kernel tree, merging multiple configurations fragments to produce a complete
 # .config, with unspecified values filled in as for alldefconfig.
@@ -37,7 +39,8 @@
 #
 # conf3 contents:
 #
-#     # Ops... assigned twice
+#     # Assigned twice (would generate warning if 'warn_assign_override' was
+#     # True)
 #     # CONFIG_FOO is not set
 #
 #     # Ops... this symbol doesn't exist
@@ -54,15 +57,20 @@
 # Running:
 #
 #     $ python(3) merge_config.py Kconfig merged conf1 conf2 conf3 conf4
-#     conf3:2: warning: FOO (defined at Kconfig:1) set more than once. Old value: "y", new value: "n".
-#     conf3:5: warning: attempt to assign the value "y" to the undefined symbol OPS
-#     warning: QAZ (defined at Kconfig:10) was assigned the value "y" but got the value "n" -- check dependencies
+#     Merged configuration 'conf1'
+#     Merged configuration 'conf2'
+#     conf3:5: warning: attempt to assign the value 'y' to the undefined symbol OPS
+#     Merged configuration 'conf3'
+#     Merged configuration 'conf4'
+#     Configuration saved to 'merged'
+#     warning: QAZ (defined at Kconfig:10) was assigned the value 'y' but got the value 'n' -- check dependencies
 #     $ cat merged
 #     Generated by Kconfiglib (https://github.com/ulfalizer/Kconfiglib)
 #     # CONFIG_FOO is not set
 #     CONFIG_BAR=y
 #     CONFIG_BAZ="baz string"
 
+from __future__ import print_function
 import sys
 
 from kconfiglib import Kconfig, BOOL, TRISTATE, TRI_TO_STR
@@ -86,12 +94,13 @@
 kconf.disable_override_warnings()
 kconf.disable_redun_warnings()
 
-# Create a merged configuration by loading the fragments with replace=False
+# Create a merged configuration by loading the fragments with replace=False.
+# load_config() and write_config() returns a message to print.
 for config in sys.argv[3:]:
-    kconf.load_config(config, replace=False)
+    print(kconf.load_config(config, replace=False))
 
 # Write the merged configuration
-kconf.write_config(sys.argv[2])
+print(kconf.write_config(sys.argv[2]))
 
 # Print warnings for symbols whose actual value doesn't match the assigned
 # value
@@ -119,5 +128,6 @@ def name_and_loc(sym):
 
         if user_value != sym.str_value:
             print("warning: {} was assigned the value '{}' but got the "
-                  "value '{}' -- check dependencies"
-                  .format(name_and_loc(sym), user_value, sym.str_value))
+                  "value '{}' -- check dependencies".format(
+                      name_and_loc(sym), user_value, sym.str_value),
+                  file=sys.stderr)

genconfig.py

@@ -77,7 +77,7 @@ def main():
 
 
     kconf = kconfiglib.Kconfig(args.kconfig_filename)
-    kconf.load_config(verbose=False)
+    kconf.load_config()
 
     kconf.write_autoconf(args.header_path)
 

guiconfig.py

@@ -175,12 +175,12 @@ def menuconfig(kconf):
 
     _create_ui()
 
-    # Load existing configuration and check if it's outdated
-    _set_conf_changed(_load_config())
-
     # Filename to save configuration to
     _conf_filename = standard_config_filename()
 
+    # Load existing configuration and check if it's outdated
+    _set_conf_changed(_load_config())
+
     # Filename to save minimal configuration to
     _minconf_filename = "defconfig"
 
@@ -238,7 +238,8 @@ def _load_config():
     # Returns True if .config is missing or outdated. We always prompt for
     # saving the configuration in that case.
 
-    if not _kconf.load_config():
+    print(_kconf.load_config())
+    if not os.path.exists(_conf_filename):
         # No .config
         return True
 
@@ -639,7 +640,8 @@ def _set_conf_changed(changed):
     global _conf_changed
 
     _conf_changed = changed
-    _set_status("Modified" if changed else "")
+    if changed:
+        _set_status("Modified")
 
 
 def _update_tree():
@@ -1341,7 +1343,6 @@ def _save(_=None):
 
     if _try_save(_kconf.write_config, _conf_filename, "configuration"):
         _set_conf_changed(False)
-        _set_status("Configuration saved to " + _conf_filename)
 
     _tree.focus_set()
 
@@ -1363,7 +1364,6 @@ def _save_as():
             break
 
         if _try_save(_kconf.write_config, filename, "configuration"):
-            _set_status("Configuration saved to " + filename)
             _conf_filename = filename
             break
 
@@ -1433,7 +1433,6 @@ def _open(_=None):
 
             _update_tree()
 
-            _set_status("Configuration loaded from " + filename)
             break
 
     _tree.focus_set()
@@ -1694,8 +1693,10 @@ def _try_save(save_fn, filename, description):
     #   String describing the thing being saved
 
     try:
-        save_fn(filename)
-        print("{} saved to '{}'".format(description, filename))
+        # save_fn() returns a message to print
+        msg = save_fn(filename)
+        _set_status(msg)
+        print(msg)
         return True
     except (OSError, IOError) as e:
         messagebox.showerror(
@@ -1714,8 +1715,9 @@ def _try_load(filename):
     #   Configuration file to load
 
     try:
-        _kconf.load_config(filename)
-        print("configuration loaded from " + filename)
+        msg = _kconf.load_config(filename)
+        _set_status(msg)
+        print(msg)
         return True
     except (OSError, IOError) as e:
         messagebox.showerror(