Resolve "Text data type does not delete as expected" (#68)

* Adjust check for zero-length ranges and rename variables

Fixes #67

* Remove variable assignment for inserted value length

* Add, document and reorder convenience methods for text manipulation

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Revert "Remove variable assignment for inserted value length"

This reverts commit cebe3d5.

* Combine deletion and insertion into a single-line replacement

* Have the slice check returning a slice again

The range length is computed outside/after the slice check

* Add and adjust tests for insertion and deletion

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Revert changes on manipulation methods, but keep docstrings

* Add test for single character replacements

---------

Co-authored-by: Jakob Zahn <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

python/pycrdt/text.py

@@ -72,11 +72,11 @@ def _check_slice(self, key: slice) -> tuple[int, int]:
         else:
             start = key.start
         if key.stop is None:
-            stop = len(self) - start
+            stop = len(self)
         elif key.stop < 0:
             raise RuntimeError("Negative stop not supported")
         else:
-            stop = key.stop - start
+            stop = key.stop
         return start, stop
 
     def __delitem__(self, key: int | slice) -> None:
@@ -86,8 +86,9 @@ def __delitem__(self, key: int | slice) -> None:
                 self.integrated.remove_range(txn._txn, key, 1)
             elif isinstance(key, slice):
                 start, stop = self._check_slice(key)
-                if start != stop:
-                    self.integrated.remove_range(txn._txn, start, stop)
+                length = stop - start
+                if length > 0:
+                    self.integrated.remove_range(txn._txn, start, length)
             else:
                 raise RuntimeError(f"Index not supported: {key}")
 
@@ -104,17 +105,20 @@ def __setitem__(self, key: int | slice, value: str) -> None:
                 self.integrated.insert(txn._txn, key, value)
             elif isinstance(key, slice):
                 start, stop = self._check_slice(key)
-                if start != stop:
-                    self.integrated.remove_range(txn._txn, start, stop)
+                length = stop - start
+                if length > 0:
+                    self.integrated.remove_range(txn._txn, start, length)
                 self.integrated.insert(txn._txn, start, value)
             else:
                 raise RuntimeError(f"Index not supported: {key}")
 
     def clear(self) -> None:
+        """Remove the entire range of characters."""
         del self[:]
 
-    def insert(self, index, text: str) -> None:
-        self[index:index] = text
+    def insert(self, index: int, value: str) -> None:
+        """Insert 'value' at character position 'index'."""
+        self[index:index] = value
 
     def observe(self, callback: Callable[[Any], None]) -> str:
         _callback = partial(observe_callback, callback, self.doc)

tests/test_text.py

@@ -2,6 +2,7 @@
 
 hello = "Hello"
 world = ", World"
+sir = " Sir"
 punct = "!"
 
 
@@ -37,8 +38,24 @@ def test_api():
     assert len(text) == 0
     text[:] = hello + world + punct
     assert str(text) == hello + world + punct
-    text[len(hello) : len(hello) + len(world)] = " Sir"
-    assert str(text) == hello + " Sir" + punct
+    text[len(hello) : len(hello) + len(world)] = sir
+    assert str(text) == hello + sir + punct
+    # single character replacement
+    text[len(text) - 1] = "?"
+    assert str(text) == hello + sir + "?"
+    # deletion with only an index
+    del text[len(text) - 1]
+    assert str(text) == hello + sir
+    # deletion of an arbitrary range
+    del text[len(hello) : len(hello) + len(sir)]
+    assert str(text) == hello
+    # deletion with start index == range length
+    text += str(text)
+    del text[len(hello) : 2 * len(hello)]
+    assert str(text) == hello
+    # deletion with a range of 0
+    del text[len(hello) : len(hello)]
+    assert str(text) == hello
 
 
 def test_to_py():