BUG: revise string_from_pyobj/try_pyarr_from_string usages, fixes #18431.

1 files changed, 144 insertions, 2 deletions

diff --git a/numpy/f2py/tests/test_string.py b/numpy/f2py/tests/test_string.py
index e3ec96af9..2a0945934 100644
--- a/numpy/f2py/tests/test_string.py
+++ b/numpy/f2py/tests/test_string.py
@@ -1,6 +1,6 @@
 import os
 import pytest
-
+import textwrap
 from numpy.testing import assert_array_equal
 import numpy as np
 from . import util
@@ -9,14 +9,156 @@ from . import util
 def _path(*a):
     return os.path.join(*((os.path.dirname(__file__),) + a))
 
+
 class TestString(util.F2PyTest):
     sources = [_path('src', 'string', 'char.f90')]
 
     @pytest.mark.slow
     def test_char(self):
         strings = np.array(['ab', 'cd', 'ef'], dtype='c').T
-        inp, out = self.module.char_test.change_strings(strings, strings.shape[1])
+        inp, out = self.module.char_test.change_strings(strings,
+                                                        strings.shape[1])
         assert_array_equal(inp, strings)
         expected = strings.copy()
         expected[1, :] = 'AAA'
         assert_array_equal(out, expected)
+
+
+class TestDocStringArguments(util.F2PyTest):
+    suffix = '.f'
+
+    code = textwrap.dedent("""
+C FILE: STRING.F
+      SUBROUTINE FOO(A,B,C,D)
+      CHARACTER*5 A, B
+      CHARACTER*(*) C,D
+Cf2py intent(in) a,c
+Cf2py intent(inout) b,d
+      PRINT*, "A=",A
+      PRINT*, "B=",B
+      PRINT*, "C=",C
+      PRINT*, "D=",D
+      PRINT*, "CHANGE A,B,C,D"
+      A(1:1) = 'A'
+      B(1:1) = 'B'
+      C(1:1) = 'C'
+      D(1:1) = 'D'
+      PRINT*, "A=",A
+      PRINT*, "B=",B
+      PRINT*, "C=",C
+      PRINT*, "D=",D
+      END
+C END OF FILE STRING.F
+        """)
+
+    def test_example(self):
+        a = np.array(b'123\0\0')
+        b = np.array(b'123\0\0')
+        c = np.array(b'123')
+        d = np.array(b'123')
+
+        self.module.foo(a, b, c, d)
+
+        assert a.tobytes() == b'123\0\0'
+        assert b.tobytes() == b'B23\0\0', (b.tobytes(),)
+        assert c.tobytes() == b'123'
+        assert d.tobytes() == b'D23'
+
+
+class TestFixedString(util.F2PyTest):
+    suffix = '.f90'
+
+    code = textwrap.dedent("""
+       function sint(s) result(i)
+          implicit none
+          character(len=*) :: s
+          integer :: j, i
+          i = 0
+          do j=1, len(s)
+           i = i + ichar(s(j:j)) * 10 ** (j - 1)
+          end do
+          return
+        end function sint
+
+        function test_in_bytes4(a) result (i)
+          implicit none
+          integer :: sint
+          character(len=4) :: a
+          integer :: i
+          i = sint(a)
+          a(1:1) = 'A'
+          return
+        end function test_in_bytes4
+
+        function test_inout_bytes4(a) result (i)
+          implicit none
+          integer :: sint
+          character(len=4), intent(inout) :: a
+          integer :: i
+          if (ichar(a(1:1)).ne.0) then
+            a(1:1) = 'E'
+          endif
+          i = sint(a)
+          return
+        end function test_inout_bytes4
+        """)
+
+    @staticmethod
+    def _sint(s, start=0, end=None):
+        """Return the content of a string buffer as integer value.
+
+        For example:
+          _sint('1234') -> 4321
+          _sint('123A') -> 17321
+        """
+        if isinstance(s, np.ndarray):
+            s = s.tobytes()
+        elif isinstance(s, str):
+            s = s.encode()
+        assert isinstance(s, bytes)
+        if end is None:
+            end = len(s)
+        i = 0
+        for j in range(start, min(end, len(s))):
+            i += s[j] * 10 ** j
+        return i
+
+    def _get_input(self, intent='in'):
+        if intent in ['in']:
+            yield ''
+            yield '1'
+            yield '1234'
+            yield '12345'
+            yield b''
+            yield b'\0'
+            yield b'1'
+            yield b'\01'
+            yield b'1\0'
+            yield b'1234'
+            yield b'12345'
+        yield np.ndarray((), np.bytes_, buffer=b'')  # array(b'', dtype='|S0')
+        yield np.array(b'')                          # array(b'', dtype='|S1')
+        yield np.array(b'\0')
+        yield np.array(b'1')
+        yield np.array(b'1\0')
+        yield np.array(b'\01')
+        yield np.array(b'1234')
+        yield np.array(b'123\0')
+        yield np.array(b'12345')
+
+    def test_intent_in(self):
+        for s in self._get_input():
+            r = self.module.test_in_bytes4(s)
+            # also checks that s is not changed inplace
+            expected = self._sint(s, end=4)
+            assert r == expected, (s)
+
+    def test_intent_inout(self):
+        for s in self._get_input(intent='inout'):
+            rest = self._sint(s, start=4)
+            r = self.module.test_inout_bytes4(s)
+            expected = self._sint(s, end=4)
+            assert r == expected
+
+            # check that the rest of input string is preserved
+            assert rest == self._sint(s, start=4)