coredata: Make warning_level per subproject builtin option

6 files changed, 54 insertions, 24 deletions

diff --git a/docs/markdown/Builtin-options.md b/docs/markdown/Builtin-options.md
index e7101d5..6234ecf 100644
--- a/docs/markdown/Builtin-options.md
+++ b/docs/markdown/Builtin-options.md
@@ -59,27 +59,27 @@ Options that are labeled "per machine" in the table are set per machine. See
 the [specifying options per machine](#Specifying-options-per-machine) section
 for details.
 
-| Option                               | Default value | Description                                                    | Is per machine |
-| ------                               | ------------- | -----------                                                    | -------------- |
-| auto_features {enabled, disabled, auto} | auto       | Override value of all 'auto' features                          | no             |
-| backend {ninja, vs,<br>vs2010, vs2015, vs2017, vs2019, xcode} | ninja | Backend to use                                | no             |
-| buildtype {plain, debug,<br>debugoptimized, release, minsize, custom} | debug |  Build type to use                    | no             |
-| debug                                | true          | Debug                                                          | no             |
-| default_library {shared, static, both} | shared      | Default library type                                           | no             |
-| errorlogs                            | true          | Whether to print the logs from failing tests.                  | no             |
-| install_umask {preserve, 0000-0777}  | 022           | Default umask to apply on permissions of installed files       | no             |
-| layout {mirror,flat}                 | mirror        | Build directory layout                                         | no             |
-| optimization {0, g, 1, 2, 3, s}      | 0             | Optimization level                                             | no             |
-| pkg_config_path {OS separated path}  | ''            | Additional paths for pkg-config to search before builtin paths | yes            |
-| cmake_prefix_path                    | []            | Additional prefixes for cmake to search before builtin paths   | yes            |
-| stdsplit                             | true          | Split stdout and stderr in test logs                           | no             |
-| strip                                | false         | Strip targets on install                                       | no             |
-| unity {on, off, subprojects}         | off           | Unity build                                                    | no             |
-| unity_size {>=2}                     | 4             | Unity file block size                                          | no             |
-| warning_level {0, 1, 2, 3}           | 1             | Set the warning level. From 0 = none to 3 = highest            | no             |
-| werror                               | false         | Treat warnings as errors                                       | no             |
-| wrap_mode {default, nofallback,<br>nodownload, forcefallback} | default | Wrap mode to use                            | no             |
-| force_fallback_for                   | []            | Force fallback for those dependencies                          | no             |
+| Option                               | Default value | Description                                                    | Is per machine | Is per subproject |
+| ------                               | ------------- | -----------                                                    | -------------- | ----------------- |
+| auto_features {enabled, disabled, auto} | auto       | Override value of all 'auto' features                          | no             | no                |
+| backend {ninja, vs,<br>vs2010, vs2015, vs2017, vs2019, xcode} | ninja | Backend to use                                | no             | no                |
+| buildtype {plain, debug,<br>debugoptimized, release, minsize, custom} | debug |  Build type to use                    | no             | no                |
+| debug                                | true          | Debug                                                          | no             | no                |
+| default_library {shared, static, both} | shared      | Default library type                                           | no             | yes               |
+| errorlogs                            | true          | Whether to print the logs from failing tests.                  | no             | no                |
+| install_umask {preserve, 0000-0777}  | 022           | Default umask to apply on permissions of installed files       | no             | no                |
+| layout {mirror,flat}                 | mirror        | Build directory layout                                         | no             | no                |
+| optimization {0, g, 1, 2, 3, s}      | 0             | Optimization level                                             | no             | no                |
+| pkg_config_path {OS separated path}  | ''            | Additional paths for pkg-config to search before builtin paths | yes            | no                |
+| cmake_prefix_path                    | []            | Additional prefixes for cmake to search before builtin paths   | yes            | no                |
+| stdsplit                             | true          | Split stdout and stderr in test logs                           | no             | no                |
+| strip                                | false         | Strip targets on install                                       | no             | no                |
+| unity {on, off, subprojects}         | off           | Unity build                                                    | no             | no                |
+| unity_size {>=2}                     | 4             | Unity file block size                                          | no             | no                |
+| warning_level {0, 1, 2, 3}           | 1             | Set the warning level. From 0 = none to 3 = highest            | no             | yes               |
+| werror                               | false         | Treat warnings as errors                                       | no             | yes               |
+| wrap_mode {default, nofallback,<br>nodownload, forcefallback} | default | Wrap mode to use                            | no             | no                |
+| force_fallback_for                   | []            | Force fallback for those dependencies                          | no             | no                |
 
 <a name="build-type-options"></a>
 For setting optimization levels and toggling debug, you can either set the
@@ -215,3 +215,22 @@ the command line, as there was no `build.` prefix. Similarly named fields in
 the `[properties]` section of the cross file would effect cross compilers, but
 the code paths were fairly different allowing differences in behavior to crop
 out.
+
+## Specifying options per subproject
+
+Since *0.54.0* `default_library` and `werror` built-in options can be defined
+per subproject. This is useful for example when building shared libraries in the
+main project, but static link a subproject, or when the main project must build
+with no warnings but some subprojects cannot.
+
+Most of the time this would be used either by the parent project by setting
+subproject's default_options (e.g. `subproject('foo', default_options: 'default_library=static')`),
+or by the user using the command line `-Dfoo:default_library=static`.
+
+The value is overriden in this order:
+- Value from parent project
+- Value from subproject's default_options if set
+- Value from subproject() default_options if set
+- Value from command line if set
+
+Since 0.56.0 `warning_level` can also be defined per subproject.
diff --git a/docs/markdown/snippets/per_subproject.md b/docs/markdown/snippets/per_subproject.md
new file mode 100644
index 0000000..6de6068
--- /dev/null
+++ b/docs/markdown/snippets/per_subproject.md
@@ -0,0 +1,4 @@
+## Per subproject `warning_level` option
+
+`warning_level` can now be defined per subproject, in the same way as
+`default_library` and `werror`.
diff --git a/mesonbuild/coredata.py b/mesonbuild/coredata.py
index af43b31..e2a6954 100644
--- a/mesonbuild/coredata.py
+++ b/mesonbuild/coredata.py
@@ -1182,7 +1182,7 @@ builtin_options = OrderedDict([
     ('strip',           BuiltinOption(UserBooleanOption, 'Strip targets on install', False)),
     ('unity',           BuiltinOption(UserComboOption, 'Unity build', 'off', choices=['on', 'off', 'subprojects'])),
     ('unity_size',      BuiltinOption(UserIntegerOption, 'Unity block size', (2, None, 4))),
-    ('warning_level',   BuiltinOption(UserComboOption, 'Compiler warning level to use', '1', choices=['0', '1', '2', '3'])),
+    ('warning_level',   BuiltinOption(UserComboOption, 'Compiler warning level to use', '1', choices=['0', '1', '2', '3'], yielding=False)),
     ('werror',          BuiltinOption(UserBooleanOption, 'Treat warnings as errors', False, yielding=False)),
     ('wrap_mode',       BuiltinOption(UserComboOption, 'Wrap mode', 'default', choices=['default', 'nofallback', 'nodownload', 'forcefallback'])),
     ('force_fallback_for', BuiltinOption(UserArrayOption, 'Force fallback for those subprojects', [])),
diff --git a/test cases/common/230 persubproject options/meson.build b/test cases/common/230 persubproject options/meson.build
index 20dff90..f76a70c 100644
--- a/test cases/common/230 persubproject options/meson.build
+++ b/test cases/common/230 persubproject options/meson.build
@@ -1,9 +1,11 @@
 project('persubproject options', 'c',
   default_options : ['default_library=both',
-                     'werror=true'])
+                     'werror=true',
+                     'warning_level=3'])
 
 assert(get_option('default_library') == 'both', 'Parent default_library should be "both"')
 assert(get_option('werror'))
+assert(get_option('warning_level') == '3')
 
 # Check it build both by calling a method only both_libraries target implement
 lib = library('lib1', 'foo.c')
diff --git a/test cases/common/230 persubproject options/subprojects/sub1/foo.c b/test cases/common/230 persubproject options/subprojects/sub1/foo.c
index 63e4de6..82ad2c2 100644
--- a/test cases/common/230 persubproject options/subprojects/sub1/foo.c
+++ b/test cases/common/230 persubproject options/subprojects/sub1/foo.c
@@ -1,5 +1,8 @@
 int foo(void);
 
 int foo(void) {
+  /* This is built with -Werror, it would error if warning_level=3 was inherited
+   * from main project and not overridden by this subproject's default_options. */
+  int x;
   return 0;
 }
diff --git a/test cases/common/230 persubproject options/subprojects/sub1/meson.build b/test cases/common/230 persubproject options/subprojects/sub1/meson.build
index 7afc934..4e4bc1b 100644
--- a/test cases/common/230 persubproject options/subprojects/sub1/meson.build
+++ b/test cases/common/230 persubproject options/subprojects/sub1/meson.build
@@ -1,6 +1,8 @@
-project('sub1', 'c')
+project('sub1', 'c',
+ default_options : ['warning_level=0'])
 
 assert(get_option('default_library') == 'both', 'Should inherit parent project default_library')
+assert(get_option('warning_level') == '0')
 
 # Check it build both by calling a method only both_libraries target implement
 lib = library('lib1', 'foo.c')