[substitutions] !include ${filename}, Substitutions in include filename paths (package refactor part 5) (#12213)

Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

esphome/expression.py

@@ -0,0 +1,25 @@
+"""Helpers for detecting substitution variables and Jinja expressions."""
+
+import re
+
+from esphome.const import VALID_SUBSTITUTIONS_CHARACTERS
+
+SUBSTITUTION_VARIABLE_PROG = re.compile(
+    rf"\$([{VALID_SUBSTITUTIONS_CHARACTERS}]+|\{{[{VALID_SUBSTITUTIONS_CHARACTERS}]*\}})"
+)
+
+_JINJA_RE = re.compile(
+    r"<%.+?%>"  # Block: <% ... %>
+    r"|\$\{[^}]+\}",  # Braced: ${ ... }
+    flags=re.MULTILINE,
+)
+
+
+def has_jinja(value: str) -> bool:
+    """Check if a string contains Jinja expressions."""
+    return _JINJA_RE.search(value) is not None
+
+
+def has_substitution_or_expression(value: str) -> bool:
+    """Check if a string contains substitution variables ($name, ${name}) or Jinja expressions."""
+    return SUBSTITUTION_VARIABLE_PROG.search(value) is not None or has_jinja(value)