Add documentation for name_prefix, name_suffix and lan_args dictionaries

docs/markdown/Reference-manual.md

@@ -479,7 +479,11 @@ be passed to [shared and static libraries](#library).
 
 - `<languagename>_pch` precompiled header file to use for the given language
 - `<languagename>_args` compiler flags to use for the given language;
-  eg: `cpp_args` for C++
+  eg: `cpp_args` for C++. Since *0.49.0* it can be a dictionary mapping target
+  type to an array of args, the value mapped to the current build type will be
+  used. For example passing `c_args: {'static_library': '-DSTATIC'}` means that
+  if a static library is built `STATIC` is defined, but not for shared
+  libraries, executables, etc.
 - `build_by_default` causes, when set to true, to have this target be
   built by default, that is, when invoking plain `ninja`, the default
   value is true for all built target types, since 0.38.0
@@ -564,6 +568,7 @@ creating the final list.
 The returned object also has methods that are documented in the
 [object methods section](#build-target-object) below.
 
+
 ### find_library()
 
 This function is deprecated and in the 0.31.0 release it was moved to
@@ -1035,16 +1040,24 @@ The keyword arguments for this are the same as for
 - `name_prefix` the string that will be used as the prefix for the
   target output filename by overriding the default (only used for
   libraries). By default this is `lib` on all platforms and compilers
-  except with MSVC shared libraries where it is omitted to follow
-  convention.
+  except with MSVCshared libraries where it is omitted to follow
+  convention. Since *0.49.0* it can be a dictionary mapping target type to a
+  string, the value mapped to the current build type will be used. For example
+  passing `name_prefix: {'static_library': 'lib'}` means that if a static
+  library is built `name_prefix` is `lib`, but for shared library `name_prefix`
+  is undefined and thus the default value is used.
 - `name_suffix` the string that will be used as the suffix for the
   target output filename by overriding the default (see also:
   [executable()](#executable)). By default, for shared libraries this
   is `dylib` on macOS, `dll` on Windows, and `so` everywhere else.
   For static libraries, it is `a` everywhere. By convention MSVC
   static libraries use the `lib` suffix, but we use `a` to avoid a
   potential name clash with shared libraries which also generate
-  `xxx.lib` import files.
+  `xxx.lib` import files. Since *0.49.0* it can be a dictionary mapping target
+  type to a string, the value mapped to the current build type will be used.
+  For example passing `name_suffix: {'static_library': 'a'}` means that if a
+  static library is built `name_suffix` is `a`, but for shared library
+  `name_suffix` is undefined and thus the default value is used.
 - `rust_crate_type` specifies the crate type for Rust
   libraries. Defaults to `dylib` for shared libraries and `rlib` for
   static libraries.

docs/markdown/snippets/target_type_dict.md

@@ -0,0 +1,26 @@
+## Dictionary for `name_prefix`, `name_suffix` and `<lang>_args`
+
+`name_prefix`, `name_suffix` and `<lang>_args` keyword arguments of functions
+like `library()` and `build_target()` now accept a dictionary mapping the target
+type to the value. This is used when for example different c_args must be passed
+to the static and shared library built by `both_libraries()`.
+
+```meson
+cargs = {
+  'static_library': '-DSTATIC',
+  'shared_library': '-DSHARED',
+  'executable': ['-DEXECUTABLE', '-DMY_APP'],
+ }
+namesuffix = {
+  'static_library': 'a',
+  'shared_library': 'so',
+}
+# sources will be built twice with different cflags, the static library will
+# have .a extension on all platforms and the shared library will have the .so
+# extension on all platforms
+both_libraries('foo', sources, c_args: cargs, name_suffix: namesuffix)
+# EXECUTABLE and MY_APP will be defined when building sources, and it will use
+# the default extension on the current platform because 'executable' is not in
+# the namesuffix dictionary
+executable('app', c_args: cargs, name_suffix: namesuffix)
+```