Merge pull request #18181 from pearu/pearu/17859

ENH: [f2py] Add external attribute support.

2 files changed, 33 insertions, 0 deletions

diff --git a/numpy/f2py/crackfortran.py b/numpy/f2py/crackfortran.py
index 16a9a6fab..d27845796 100755
--- a/numpy/f2py/crackfortran.py
+++ b/numpy/f2py/crackfortran.py
@@ -1611,6 +1611,10 @@ def updatevars(typespec, selector, attrspec, entitydecl):
             edecl['charselector'] = copy.copy(charselect)
             edecl['typename'] = typename
             edecl['attrspec'] = copy.copy(attrspec)
+        if 'external' in (edecl.get('attrspec') or []) and e in groupcache[groupcounter]['args']:
+            if 'externals' not in groupcache[groupcounter]:
+                groupcache[groupcounter]['externals'] = []
+            groupcache[groupcounter]['externals'].append(e)
         if m.group('after'):
             m1 = lenarraypattern.match(markouterparen(m.group('after')))
             if m1:
diff --git a/numpy/f2py/tests/test_crackfortran.py b/numpy/f2py/tests/test_crackfortran.py
index 735804024..827c71ae9 100644
--- a/numpy/f2py/tests/test_crackfortran.py
+++ b/numpy/f2py/tests/test_crackfortran.py
@@ -86,3 +86,32 @@ class TestPublicPrivate():
         assert 'public' not in mod['vars']['a']['attrspec']
         assert 'private' not in mod['vars']['seta']['attrspec']
         assert 'public' in mod['vars']['seta']['attrspec']
+
+class TestExternal(util.F2PyTest):
+    # issue gh-17859: add external attribute support
+    code = """
+        integer(8) function external_as_statement(fcn)
+        implicit none
+        external fcn
+        integer(8) :: fcn
+        external_as_statement = fcn(0)
+        end
+
+        integer(8) function external_as_attribute(fcn)
+        implicit none
+        integer(8), external :: fcn
+        external_as_attribute = fcn(0)
+        end
+    """
+
+    def test_external_as_statement(self):
+        def incr(x):
+            return x + 123
+        r = self.module.external_as_statement(incr)
+        assert r == 123
+
+    def test_external_as_attribute(self):
+        def incr(x):
+            return x + 123
+        r = self.module.external_as_attribute(incr)
+        assert r == 123