meson: add .has_external_property() methods

Useful in case of boolean values to distinguish between a boolean
value having been set in the native/cross file and not having been
provided, which can't be achieved by passing a fallback parameter
to .get_external_property().

2 files changed, 14 insertions, 0 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 6669530..b0f5032 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -1991,6 +1991,13 @@ the following methods.
   If `native: false` or not specified, variable is retrieved from the
   cross-file if cross-compiling, and from the native-file when not cross-compiling.
 
+- `has_external_property(propname, native: true/false)`
+  *(since 0.58.0)*: checks whether the given property exist in a native or
+  cross file. The optional `native: true` forces checking for the variable
+  in the native file, even when cross-compiling.
+  If `native: false` or not specified, the variable is checked for in the
+  cross-file if cross-compiling, and in the native-file when not cross-compiling.
+
 - `can_run_host_binaries()` *(since 0.55.0)*: returns true if the build machine can run
   binaries compiled for the host. This returns true unless you are
   cross compiling, need a helper to run host binaries, and don't have one.
diff --git a/docs/markdown/snippets/has_external_property.md b/docs/markdown/snippets/has_external_property.md
new file mode 100644
index 0000000..8a815d7
--- /dev/null
+++ b/docs/markdown/snippets/has_external_property.md
@@ -0,0 +1,7 @@
+## Check if native or cross-file properties exist
+
+It is now possible to check whether a native property or a cross-file property
+exists with `meson.has_external_property('foo')`. This is useful if the
+property in question is a boolean and one wants to distinguish between
+"set" and "not provided" which can't be done the usual way by passing a
+fallback parameter to `meson.get_external_property()` in this particular case.