3 files changed, 39 insertions, 1 deletions
diff --git a/docs/markdown/Fs-module.md b/docs/markdown/Fs-module.md
index e68bf68..3332b1e 100644
--- a/docs/markdown/Fs-module.md
+++ b/docs/markdown/Fs-module.md
@@ -8,6 +8,8 @@ available starting with version 0.53.0.
 Non-absolute paths are looked up relative to the directory where the
 current `meson.build` file is.
 
+If specified, `~` is expanded to the user home directory.
+
 ### exists
 
 Takes a single string argument and returns true if an entity with that
@@ -29,3 +31,16 @@ name exists on the file system. This method follows symbolic links.
 
 Takes a single string argument and returns true if the path pointed to
 by the string is a symbolic link.
+
+## Filename modification
+
+### with_suffix
+
+The `with_suffix` method allows changing the filename suffix
+
+```meson
+original = '/opt/foo.ini'
+new = fs.with_suffix('.txt')
+```
+
+The files need not actually exist yet for this method.
+\ No newline at end of file
diff --git a/mesonbuild/modules/fs.py b/mesonbuild/modules/fs.py
index a9881c4..1687d0d 100644
--- a/mesonbuild/modules/fs.py
+++ b/mesonbuild/modules/fs.py
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import typing
-from pathlib import Path
+from pathlib import Path, PurePath
 
 from . import ExtensionModule
 from . import ModuleReturnValue
@@ -55,5 +55,15 @@ class FSModule(ExtensionModule):
     def is_dir(self, state: 'ModuleState', args: typing.Sequence[str], kwargs: dict) -> ModuleReturnValue:
         return self._check('is_dir', state, args)
 
+    @stringArgs
+    @noKwargs
+    def with_suffix(self, state: 'ModuleState', args: typing.Sequence[str], kwargs: dict) -> ModuleReturnValue:
+        if len(args) != 2:
+            MesonException('method takes exactly two arguments.')
+        original = PurePath(state.source_root) / state.subdir / args[0]
+        new = original.with_suffix(args[1])
+        return ModuleReturnValue(str(new), [])
+
+
 def initialize(*args, **kwargs) -> FSModule:
     return FSModule(*args, **kwargs)
diff --git a/test cases/common/227 fs module/meson.build b/test cases/common/227 fs module/meson.build
index 30d193f..fcb08c0 100644
--- a/test cases/common/227 fs module/meson.build
+++ b/test cases/common/227 fs module/meson.build
@@ -21,4 +21,17 @@ assert(not fs.is_dir('nonexisting'), 'Bad path detected as a dir.')
 assert(fs.is_dir('~'), 'expanduser not working')
 assert(not fs.is_file('~'), 'expanduser not working')
 
+original = 'foo.txt'
+new = fs.with_suffix(original, '.ini')
+assert(new.endswith('foo.ini') and not new.contains('.txt'), 'with_suffix failed')
+
+if build_machine.system() != 'windows'
+  # this feature works on Windows, but `/` on windows is interpreted like `.drive` which in general may not be `c:/`
+  # so we omit this from self-test on Windows
+
+  original = '/opt/foo.txt'
+  new = fs.with_suffix(original, '.ini')
+  assert(new == '/opt/foo.ini', 'absolute path with_suffix failed')
+endif
+
 subdir('subdir')