lib: Accept more newline styles in G_getl (#3853)

Use G_getl2 in G_getl to have everywhere the same behavior of supporting all newlines. Originally, G_getl2 was created to keep the behavior of G_getl. However, now, we want G_getl2 behavior everywhere.

Keeping G_getl2 for compatibility. Code can later be clean up to use only G_getl, probably at the time when G_getl2 is removed (v9).

The new test fails without the change in the library for CRLF for G_getl, but passes with the change. CR fails because it is not supported by fgets used since 88090da (#3850), so expecting failure for CR.

Return and argument types for ctypes fopen need to be set for the code to work everywhere reliably.

---------

Co-authored-by: Nicklas Larsson <[email protected]>

lib/gis/getl.c

@@ -19,32 +19,26 @@
  * \brief Gets a line of text from a file
  *
  * This routine runs fgets() to fetch a line of text from a file
- * (advancing file pointer) and removes trailing newline. fgets() does
- * not recognize '<code>\\r</code>' as an EOL and will read past * it.
+ * (advancing file pointer) and removes trailing newline.
  *
  * \param buf string buffer to receive read data
  * \param n maximum number of bytes to read
  * \param fd file descriptor structure
  *
  * \return 1 on success
  * \return 0 EOF
+ *
+ * \see G_getl2()
  */
 int G_getl(char *buf, int n, FILE *fd)
 {
-    if (!fgets(buf, n, fd))
-        return 0;
-
-    for (; *buf && *buf != '\n'; buf++)
-        ;
-    *buf = 0;
-
-    return 1;
+    return G_getl2(buf, n, fd);
 }
 
 /*!
  * \brief Gets a line of text from a file of any pedigree
  *
- * This routine is like G_getl() but is more portable.  It supports
+ * This routine supports
  * text files created on various platforms (UNIX, MacOS9, DOS),
  * i.e. <code>\\n (\\012)</code>, <code>\\r (\\015)</code>, and
  * <code>\\r\\n (\\015\\012)</code> style newlines.

lib/gis/testsuite/test_gis_lib_getl.py

@@ -0,0 +1,81 @@
+"""Test of gis library line reading functions
+
+@author Vaclav Petras
+"""
+
+import ctypes
+import pathlib
+import platform
+import unittest
+
+import grass.lib.gis as libgis
+from grass.gunittest.case import TestCase
+from grass.gunittest.main import test
+
+
+class TestNewlinesWithGetlFunctions(TestCase):
+    """Test C functions G_getl() and G_getl2() from gis library"""
+
+    @classmethod
+    def setUpClass(cls):
+        cls.libc = ctypes.cdll.LoadLibrary(ctypes.util.find_library("c"))
+        cls.libc.fopen.restype = ctypes.POINTER(libgis.FILE)
+        cls.libc.fopen.argtypes = [ctypes.c_char_p, ctypes.c_char_p]
+        cls.file_path = pathlib.Path("test.txt")
+
+    def tearDown(self):
+        self.file_path.unlink()
+
+    def read_lines_and_assert(self, get_line_function, newline):
+        """Write and read lines and then assert they are as expected"""
+        lines = ["Line 1", "Line 2", "Line 3"]
+        with open(self.file_path, mode="w", newline=newline) as stream:
+            for line in lines:
+                # Python text newline here.
+                # The specific newline is added by the stream.
+                stream.write(f"{line}\n")
+
+        file_ptr = self.libc.fopen(str(self.file_path).encode("utf-8"), b"r")
+        if not file_ptr:
+            raise FileNotFoundError(f"Could not open file: {self.file_path}")
+
+        try:
+            buffer_size = 50
+            buffer = ctypes.create_string_buffer(buffer_size)
+
+            for line in lines:
+                get_line_function(buffer, ctypes.sizeof(buffer), file_ptr)
+                result = buffer.value.decode("utf-8") if buffer else None
+                self.assertEqual(line, result)
+        finally:
+            self.libc.fclose(file_ptr)
+
+    def test_getl_lf(self):
+        r"""Check G_getl() with LF (\n)"""
+        self.read_lines_and_assert(libgis.G_getl, "\n")
+
+    @unittest.expectedFailure
+    def test_getl_cr(self):
+        r"""Check G_getl() with CR (\r)"""
+        self.read_lines_and_assert(libgis.G_getl, "\r")
+
+    def test_getl_crlf(self):
+        r"""Check G_getl() with CRLF (\r\n)"""
+        self.read_lines_and_assert(libgis.G_getl, "\r\n")
+
+    def test_getl2_lf(self):
+        r"""Check G_getl2() with LF (\n)"""
+        self.read_lines_and_assert(libgis.G_getl2, "\n")
+
+    @unittest.expectedFailure
+    def test_getl2_cr(self):
+        r"""Check G_getl2() with CR (\r)"""
+        self.read_lines_and_assert(libgis.G_getl2, "\r")
+
+    def test_getl2_crlf(self):
+        r"""Check G_getl2() with CRLF (\r\n)"""
+        self.read_lines_and_assert(libgis.G_getl2, "\r\n")
+
+
+if __name__ == "__main__":
+    test()