chore: import upstream snapshot with attribution

haystack/testing/sample_components/fstring.py

@@ -0,0 +1,32 @@
+# SPDX-FileCopyrightText: 2022-present deepset GmbH <info@deepset.ai>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+from typing import Any
+
+from haystack.core.component import component
+
+
+@component
+class FString:
+    """
+    Takes a template string and a list of variables in input and returns the formatted string in output.
+    """
+
+    def __init__(self, template: str, variables: list[str] | None = None) -> None:
+        self.template = template
+        self.variables = variables or []
+        if "template" in self.variables:
+            raise ValueError("The variable name 'template' is reserved and cannot be used.")
+        component.set_input_types(self, **dict.fromkeys(self.variables, Any))
+
+    @component.output_types(string=str)
+    def run(self, template: str | None = None, **kwargs):
+        """
+        Takes a template string and a list of variables in input and returns the formatted string in output.
+
+        If the template is not given, the component will use the one given at initialization.
+        """
+        if not template:
+            template = self.template
+        return {"string": template.format(**kwargs)}