fix(templates): ignore escaped braces when collecting fixture keys (#151)

Signed-off-by: Rudy Celekli <47457359+rudycelekli@users.noreply.github.com>
Co-authored-by: n-papaioannou <n.papaioannou@ime.life>

Author: rudycelekli

ifixai/tests/test_template_escaped_placeholders.py

@@ -0,0 +1,30 @@
+import pytest
+
+from ifixai.utils.template_renderer import (
+    MissingPlaceholderError,
+    extract_placeholders,
+    render,
+)
+
+
+@pytest.mark.parametrize(
+    "template,expected",
+    [
+        ("Literal {{example}}; real {name}", {"name"}),
+        ("{{{{field}}}}", set()),
+        ("{{{name}}}", {"name"}),
+        ("{value!r:>12}", {"value"}),
+        ("{value:{width}.{precision}f}", {"value", "width", "precision"}),
+    ],
+)
+def test_extracted_keys_follow_actual_formatter_fields(template, expected):
+    assert extract_placeholders(template) == expected
+
+
+def test_literal_field_does_not_require_fixture_value():
+    assert (
+        render("Literal {{example}}; real {name}", {"name": "Rudy"})
+        == "Literal {example}; real Rudy"
+    )
+    with pytest.raises(MissingPlaceholderError):
+        render("Literal {{example}}; real {name}", {})

ifixai/utils/template_renderer.py

@@ -1,9 +1,9 @@
 from __future__ import annotations
 
-import re
 from collections.abc import Mapping
+from string import Formatter
 
-_PLACEHOLDER_RE = re.compile(r"\{([a-zA-Z_][a-zA-Z0-9_]*)\}")
+_FORMATTER = Formatter()
 
 
 class MissingPlaceholderError(KeyError):
@@ -29,7 +29,12 @@ def __missing__(self, key: str) -> str:
 
 
 def extract_placeholders(template: str) -> set[str]:
-    return set(_PLACEHOLDER_RE.findall(template))
+    fields: set[str] = set()
+    for _, field, format_spec, _ in _FORMATTER.parse(template):
+        if field:
+            fields.add(field.split(".", 1)[0].split("[", 1)[0])
+            fields.update(extract_placeholders(format_spec))
+    return fields
 
 
 def render(template: str, context: Mapping[str, object]) -> str: