fix: Go To Implementation works for submodules

It is now possible for interfaces with implementations in submodules
i.e. a Function or a Subroutine

Fixes #74

CHANGELOG.md

@@ -29,6 +29,8 @@
 
 ### Fixed
 
+- Fixed bug where Go To Implementation would not work for submodules
+  ([#74](https://github.com/fortran-lang/fortls/issues/74))
 - Fixed bug where `associate` blocks for variables pointing to function results
   where not properly resolved
   ([#269](https://github.com/fortran-lang/fortls/issues/269))

fortls/langserver.py

@@ -1165,6 +1165,10 @@ def serve_implementation(self, request: dict):
             impl_obj = var_obj.link_obj
             if (impl_obj is not None) and (impl_obj.file_ast.file is not None):
                 return self._create_ref_link(impl_obj)
+        elif var_obj.parent.get_type() == INTERFACE_TYPE_ID:
+            # Find the first implementation of the interface
+            if var_obj.link_obj is not None:
+                return self._create_ref_link(var_obj.link_obj)
         return None
 
     def serve_rename(self, request: dict):

fortls/objects.py

@@ -897,6 +897,8 @@ def resolve_link(self, obj_tree):
                             if file_scope is child_old:
                                 child.file_ast.scope_list[j] = child
                     if child.get_type() == prototype.get_type():
+                        # Link the interface with the implementation
+                        prototype.link_obj = child
                         prototype.resolve_link(obj_tree)
                         child.copy_interface(prototype)
                         break
@@ -922,6 +924,7 @@ def __init__(
         self.in_children: list = []
         self.missing_args: list = []
         self.mod_scope: bool = mod_flag
+        self.link_obj: Subroutine | Function | None = None
 
     def is_mod_scope(self):
         return self.mod_scope

test/test_server_implementation.py

@@ -75,3 +75,18 @@ def test_implementation_no_file():
     errcode, results = run_request(string, ["-n", "1"])
     assert errcode == 0
     assert results[1] is None
+
+
+def test_implementation_submodule():
+    """Go to implementation for submodule"""
+    root = test_dir / "imp"
+    string = write_rpc_request(1, "initialize", {"rootPath": str(root)})
+    file_path = root / "submodule.f90"
+    string += imp_request(file_path, 5, 30)
+    string += imp_request(file_path, 8, 30)
+    string += imp_request(file_path, 9, 30)
+    errcode, results = run_request(string, ["-n", "1"])
+    assert errcode == 0
+    assert results[1] == create(str(root / "submodule.f90"), 19, 20, 34)
+    assert results[2] == create(str(root / "submodule.f90"), 19, 20, 34)
+    assert results[3] is None

test/test_source/imp/submodule.f90

@@ -0,0 +1,24 @@
+module parent_mod
+  implicit none
+  type :: typ
+    real(kind=8) :: value
+  contains
+    procedure :: method1 => submod_method1
+  end type typ
+  interface
+    module subroutine submod_method1(this)
+      class(typ), intent(inout) :: this
+    end subroutine submod_method1
+    module subroutine submod_method2(this, value)
+      class(typ), intent(inout) :: this
+      real, intent(in) :: value
+    end subroutine submod_method2
+  end interface
+end module parent_mod
+submodule(parent_mod) submod
+contains
+  module subroutine submod_method1(this)
+    class(typ), intent(inout) :: this
+    this%value = 0
+  end subroutine submod_method1
+end submodule submod