File: Add full_path() method

docs/markdown/snippets/file-full-path.md

@@ -0,0 +1,7 @@
+## File object now has `full_path()` method
+
+Returns a full path pointing to the file. This is useful for printing the path
+with e.g [[message]] function for debugging purpose.
+
+**NOTE:** In most cases using the object itself will do the same job
+as this and will also allow Meson to setup dependencies correctly.

docs/yaml/objects/file.yaml

@@ -1,3 +1,13 @@
 name: file
 long_name: File
-description: Opaque object that stores the path to an existing file
+description: Object that stores the path to an existing file
+
+methods:
+- name: full_path
+  returns: str
+  since: 1.4.0
+  description: |
+    Returns a full path pointing to the file. This is useful for printing the
+    path with e.g [[message]] function for debugging purpose.
+    **NOTE:** In most cases using the object itself will do the same job
+    as this and will also allow Meson to setup dependencies correctly.

mesonbuild/interpreter/interpreterobjects.py

@@ -701,7 +701,16 @@ class IncludeDirsHolder(ObjectHolder[build.IncludeDirs]):
     pass
 
 class FileHolder(ObjectHolder[mesonlib.File]):
-    pass
+    def __init__(self, file: mesonlib.File, interpreter: 'Interpreter'):
+        super().__init__(file, interpreter)
+        self.methods.update({'full_path': self.full_path_method,
+                             })
+
+    @noPosargs
+    @noKwargs
+    @FeatureNew('file.full_path', '1.4.0')
+    def full_path_method(self, args: T.List[TYPE_var], kwargs: TYPE_kwargs) -> str:
+        return self.held_object.absolute_path(self.env.source_dir, self.env.build_dir)
 
 class HeadersHolder(ObjectHolder[build.Headers]):
     pass

test cases/common/74 file object/meson.build

@@ -6,3 +6,9 @@ test('fobj', executable('fobj', prog0, lib0))
 
 subdir('subdir1')
 subdir('subdir2')
+
+# Use fs.as_posix() because / operator replaces \ with / in the path, but
+# full_path() method is not doing that. This is a pretty inconsistent across all
+# Meson APIs.
+fs = import('fs')
+assert(fs.as_posix(prog0[0].full_path()) == fs.as_posix(meson.current_source_dir() / 'prog.c'))