Override find_program('meson')

This override transparently upgrades anyone using it to this better
functionality.

Fixes #8511

3 files changed, 45 insertions, 0 deletions

diff --git a/docs/markdown/snippets/override-find-program-meson.md b/docs/markdown/snippets/override-find-program-meson.md
new file mode 100644
index 0000000..5d281cd
--- /dev/null
+++ b/docs/markdown/snippets/override-find-program-meson.md
@@ -0,0 +1,38 @@
+## New override of `find_program('meson')`
+
+In some cases, it has been useful for build scripts to access the Meson command
+used to invoke the build script. This has led to various ad-hoc solutions that
+can be very brittle and project-specific.
+
+```meson
+meson_prog = find_program('meson')
+```
+
+This call will supply the build script with an external program pointing at the
+invoked Meson.
+
+Because Meson also uses `find_program` for program lookups internally, this
+override will also be handled in cases similar to the following:
+
+```meson
+custom_target(
+  # ...
+  command: [
+    'meson',
+  ],
+  # ...
+)
+
+run_command(
+  'meson',
+  # ...
+)
+
+run_target(
+  'tgt',
+  command: [
+    'meson',
+    # ...
+  ]
+)
+```
diff --git a/docs/yaml/functions/find_program.yaml b/docs/yaml/functions/find_program.yaml
index c0c13d2..537bbc5 100644
--- a/docs/yaml/functions/find_program.yaml
+++ b/docs/yaml/functions/find_program.yaml
@@ -42,6 +42,9 @@ description: |
   setcap = find_program(['setcap', '/usr/sbin/setcap', '/sbin/setcap'], required : false)
   ```
 
+  *Since 1.2.0* `find_program('meson')` is automatically overridden to the Meson
+  command used to execute the build script.
+
   The returned [[@external_program]] object also has documented methods.
 
 posargs:
diff --git a/mesonbuild/interpreter/interpreter.py b/mesonbuild/interpreter/interpreter.py
index 9ca7742..81a88e5 100644
--- a/mesonbuild/interpreter/interpreter.py
+++ b/mesonbuild/interpreter/interpreter.py
@@ -1665,6 +1665,10 @@ class Interpreter(InterpreterBase, HoldableObject):
         if progobj:
             return progobj
 
+        if args[0] == 'meson':
+            # Override find_program('meson') to return what we were invoked with
+            return ExternalProgram('meson', self.environment.get_build_command(), silent=True)
+
         fallback = None
         wrap_mode = self.coredata.get_option(OptionKey('wrap_mode'))
         if wrap_mode != WrapMode.nofallback and self.environment.wrap_resolver: