1 files changed, 45 insertions, 0 deletions
diff --git a/src/prompt_toolkit/completion/deduplicate.py b/src/prompt_toolkit/completion/deduplicate.py
new file mode 100644
index 0000000..c3d5256
--- /dev/null
+++ b/src/prompt_toolkit/completion/deduplicate.py
@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from typing import Iterable
+
+from prompt_toolkit.document import Document
+
+from .base import CompleteEvent, Completer, Completion
+
+__all__ = ["DeduplicateCompleter"]
+
+
+class DeduplicateCompleter(Completer):
+    """
+    Wrapper around a completer that removes duplicates. Only the first unique
+    completions are kept.
+
+    Completions are considered to be a duplicate if they result in the same
+    document text when they would be applied.
+    """
+
+    def __init__(self, completer: Completer) -> None:
+        self.completer = completer
+
+    def get_completions(
+        self, document: Document, complete_event: CompleteEvent
+    ) -> Iterable[Completion]:
+        # Keep track of the document strings we'd get after applying any completion.
+        found_so_far: set[str] = set()
+
+        for completion in self.completer.get_completions(document, complete_event):
+            text_if_applied = (
+                document.text[: document.cursor_position + completion.start_position]
+                + completion.text
+                + document.text[document.cursor_position :]
+            )
+
+            if text_if_applied == document.text:
+                # Don't include completions that don't have any effect at all.
+                continue
+
+            if text_if_applied in found_so_far:
+                continue
+
+            found_so_far.add(text_if_applied)
+            yield completion