Support enabling the assignment-to-undef. symbol warning via the environment

This makes it possible to enable it for the bundled tools, by setting
KCONFIG_WARN_UNDEF_ASSIGN=y. Previously, the code had to be modified to
call Kconfig.enable_undef_warnings().

Also rename KCONFIG_STRICT to KCONFIG_WARN_UNDEF, for consistency. Keep
supporting KCONFIG_STRICT as an alias for backwards compatibility.

4 files changed, 66 insertions, 45 deletions

diff --git a/README.rst b/README.rst
index ea453d6..4ba2748 100644
--- a/README.rst
+++ b/README.rst
@@ -325,14 +325,28 @@ The following Kconfig extensions are available:
   caveat that they must have the same name as the environment variables they
   reference. A warning is printed if the names differ.
 
-- Setting the environment variable ``KCONFIG_STRICT`` to "y" will cause warnings to be printed
-  for all references to undefined Kconfig symbols within Kconfig files. The only gotcha is
-  that all ``hex`` literals must be prefixed by "0x" or "0X", to make it possible to distuinguish
-  them from symbol references.
-
-  Some projects (e.g. the Linux kernel) use multiple Kconfig trees with many shared ``Kconfig``
-  files, leading to some safe undefined symbol references. ``KCONFIG_STRICT`` is useful in
-  projects that only have a single ``Kconfig`` tree though.
+- Two extra optional warnings can be enabled by setting environment variables,
+  covering cases that are easily missed when making changes to Kconfig files:
+
+  * ``KCONFIG_WARN_UNDEF``: If set to ``y``, warnings will be generated for all
+    references to undefined symbols within Kconfig files. The only gotcha is
+    that all hex literals must be prefixed with ``0x`` or ``0X``, to make it
+    possible to distinguish them from symbol references.
+
+    Some projects (e.g. the Linux kernel) use multiple Kconfig trees with many
+    shared Kconfig files, leading to some safe undefined symbol references.
+    ``KCONFIG_WARN_UNDEF`` is useful in projects that only have a single
+    Kconfig tree though.
+
+    ``KCONFIG_STRICT`` is an older alias for this environment variable,
+    supported for backwards compatibility.
+
+  * ``KCONFIG_WARN_UNDEF_ASSIGN``: If set to ``y``, warnings will be generated
+    for all assignments to undefined symbols within ``.config`` files. By
+    default, no such warnings are generated.
+
+    This warning can also be enabled/disabled via
+    ``Kconfig.enable/disable_undef_warnings()``.
 
 Other features
 --------------
diff --git a/kconfiglib.py b/kconfiglib.py
index e197de4..63822f1 100644
--- a/kconfiglib.py
+++ b/kconfiglib.py
@@ -415,18 +415,30 @@ def_tristate, allowing int, hex, and string symbols to be given a type and a
 default at the same time.
 
 
-Warnings for undefined symbols
-------------------------------
+Extra optional warnings
+-----------------------
 
-Setting the environment variable KCONFIG_STRICT to "y" will cause warnings to
-be printed for all references to undefined Kconfig symbols within Kconfig
-files. The only gotcha is that all hex literals must be prefixed by "0x" or
-"0X", to make it possible to distuinguish them from symbol references.
+Some optional warnings can be controlled via environment variables:
 
-Some projects (e.g. the Linux kernel) use multiple Kconfig trees with many
-shared Kconfig files, leading to some safe undefined symbol references.
-KCONFIG_STRICT is useful in projects that only have a single Kconfig tree
-though.
+  - KCONFIG_WARN_UNDEF: If set to 'y', warnings will be generated for all
+    references to undefined symbols within Kconfig files. The only gotcha is
+    that all hex literals must be prefixed with "0x" or "0X", to make it
+    possible to distinguish them from symbol references.
+
+    Some projects (e.g. the Linux kernel) use multiple Kconfig trees with many
+    shared Kconfig files, leading to some safe undefined symbol references.
+    KCONFIG_WARN_UNDEF is useful in projects that only have a single Kconfig
+    tree though.
+
+    KCONFIG_STRICT is an older alias for this environment variable, supported
+    for backwards compatibility.
+
+  - KCONFIG_WARN_UNDEF_ASSIGN: If set to 'y', warnings will be generated for
+    all assignments to undefined symbols within .config files. By default, no
+    such warnings are generated.
+
+    This warning can also be enabled/disabled via
+    Kconfig.enable/disable_undef_warnings().
 
 
 Preprocessor user functions defined in Python
@@ -770,19 +782,9 @@ class Kconfig(object):
         KconfigError on syntax errors. Note that Kconfig files are not the same
         as .config files (which store configuration symbol values).
 
-        If the environment variable KCONFIG_STRICT is set to "y", warnings will
-        be generated for all references to undefined symbols within Kconfig
-        files. The reason this isn't the default is that some projects (e.g.
-        the Linux kernel) use multiple Kconfig trees (one per architecture)
-        with many shared Kconfig files, leading to some safe references to
-        undefined symbols.
-
-        KCONFIG_STRICT relies on literal hex values being prefixed with 0x/0X.
-        They are indistinguishable from references to undefined symbols
-        otherwise.
-
-        KCONFIG_STRICT might enable other warnings that depend on there being
-        just a single Kconfig tree in the future.
+        See the module docstring for some environment variables that influence
+        default warning settings (KCONFIG_WARN_UNDEF and
+        KCONFIG_WARN_UNDEF_ASSIGN).
 
         filename (default: "Kconfig"):
           The Kconfig file to load. For the Linux kernel, you'll want "Kconfig"
@@ -844,7 +846,8 @@ class Kconfig(object):
 
         self._warnings_enabled = warn
         self._warn_to_stderr = warn_to_stderr
-        self._warn_for_undef_assign = False
+        self._warn_for_undef_assign = \
+            os.environ.get("KCONFIG_WARN_UNDEF_ASSIGN") == "y"
         self._warn_for_redun_assign = True
 
 
@@ -978,7 +981,11 @@ class Kconfig(object):
         self._check_sym_sanity()
         self._check_choice_sanity()
 
-        if os.environ.get("KCONFIG_STRICT") == "y":
+        # KCONFIG_STRICT is an older alias for KCONFIG_WARN_UNDEF, supported
+        # for backwards compatibility
+        if os.environ.get("KCONFIG_WARN_UNDEF") == "y" or \
+           os.environ.get("KCONFIG_STRICT") == "y":
+
             self._check_undef_syms()
 
 
@@ -1621,8 +1628,8 @@ class Kconfig(object):
     def enable_undef_warnings(self):
         """
         Enables warnings for assignments to undefined symbols. Disabled by
-        default since they tend to be spammy for Kernel configurations (and
-        mostly suggests cleanups).
+        default unless the KCONFIG_WARN_UNDEF_ASSIGN environment variable was
+        set to 'y' when the Kconfig instance was created.
         """
         self._warn_for_undef_assign = True
 
diff --git a/tests/Kstrict b/tests/Kundef
index fae521a..fae521a 100644
--- a/tests/Kstrict
+++ b/tests/Kundef
diff --git a/testsuite.py b/testsuite.py
index 644c151..cca5dad 100644
--- a/testsuite.py
+++ b/testsuite.py
@@ -2518,16 +2518,16 @@ config PRINT_ME_TOO
     sys.path.pop(0)
 
 
-    print("Testing KCONFIG_STRICT")
+    print("Testing KCONFIG_WARN_UNDEF")
 
-    os.environ["KCONFIG_STRICT"] = "y"
-    c = Kconfig("Kconfiglib/tests/Kstrict", warn_to_stderr=False)
+    os.environ["KCONFIG_WARN_UNDEF"] = "y"
+    c = Kconfig("Kconfiglib/tests/Kundef", warn_to_stderr=False)
 
     verify_equal("\n".join(c.warnings), """
-warning: the int symbol INT (defined at Kconfiglib/tests/Kstrict:8) has a non-int range [UNDEF_2 (undefined), 8 (undefined)]
+warning: the int symbol INT (defined at Kconfiglib/tests/Kundef:8) has a non-int range [UNDEF_2 (undefined), 8 (undefined)]
 warning: undefined symbol UNDEF_1:
 
-- Referenced at Kconfiglib/tests/Kstrict:4:
+- Referenced at Kconfiglib/tests/Kundef:4:
 
 config BOOL
 	bool
@@ -2535,7 +2535,7 @@ config BOOL
 	default UNDEF_2
 
 
-- Referenced at Kconfiglib/tests/Kstrict:19:
+- Referenced at Kconfiglib/tests/Kundef:19:
 
 menu "menu"
 	depends on UNDEF_1
@@ -2543,7 +2543,7 @@ menu "menu"
 
 warning: undefined symbol UNDEF_2:
 
-- Referenced at Kconfiglib/tests/Kstrict:4:
+- Referenced at Kconfiglib/tests/Kundef:4:
 
 config BOOL
 	bool
@@ -2551,7 +2551,7 @@ config BOOL
 	default UNDEF_2
 
 
-- Referenced at Kconfiglib/tests/Kstrict:8:
+- Referenced at Kconfiglib/tests/Kundef:8:
 
 config INT
 	int
@@ -2561,14 +2561,14 @@ config INT
 
 warning: undefined symbol UNDEF_3:
 
-- Referenced at Kconfiglib/tests/Kstrict:19:
+- Referenced at Kconfiglib/tests/Kundef:19:
 
 menu "menu"
 	depends on UNDEF_1
 	visible if UNDEF_3
 """[1:])
 
-    os.environ.pop("KCONFIG_STRICT")
+    os.environ.pop("KCONFIG_WARN_UNDEF")
 
 
     print("\nAll selftests passed\n" if all_passed else