Add support for passing flags as strings

resolves #51

There is no support for `Flags` structs as provided by the `regress`
crate. But a string can be passed down and is converted to Flags by
the `with_flags` constructor.
Exposing flags as a struct/enum adds significant complexity deemed
not worth the additional code at this time.
(See #51 for more details.)

A python test verifies that the alternate constructor pattern works
and provides support for the `"u"` flag.

src/lib.rs

@@ -12,10 +12,17 @@ struct RegexPy {
 #[pymethods]
 impl RegexPy {
     #[new]
-    fn init(value: &str) -> PyResult<Self> {
-        match Regex::new(value) {
-            Ok(inner) => Ok(RegexPy { inner }),
-            Err(e) => Err(RegressError::new_err(e.to_string())),
+    #[pyo3(signature = (value, flags=None))]
+    fn init(value: &str, flags: Option<&str>) -> PyResult<Self> {
+        match flags {
+            Some(f) => match Regex::with_flags(value, f) {
+                Ok(inner) => Ok(RegexPy { inner }),
+                Err(e) => Err(RegressError::new_err(e.to_string())),
+            },
+            None => match Regex::new(value) {
+                Ok(inner) => Ok(RegexPy { inner }),
+                Err(e) => Err(RegressError::new_err(e.to_string())),
+            },
         }
     }
 

tests/test_regress.py

@@ -1,5 +1,4 @@
 import pytest
-
 import regress
 
 
@@ -60,3 +59,16 @@ def test_error_handling():
         pass
     else:
         pytest.fail("error not reached")
+
+
+def test_with_flags():
+    # "L" for letters, "Z" for spaces, "N" for numerics
+    pattern = r"^\p{L}\p{Z}\p{N}$"
+
+    regex = regress.Regex(pattern, flags="u")
+    flagless_regex = regress.Regex(pattern)
+
+    match = regex.find("a 0")
+    flagless_match = flagless_regex.find("a 0")
+    assert match is not None
+    assert flagless_match is None