refactor: Remove duplicated escape helper logic

Author: seedspirit

src/ai/backend/common/dto/manager/v2/prometheus_query_preset/validators.py

@@ -6,22 +6,31 @@
 
 from ai.backend.common.exception import InvalidMetricPresetTemplate
 
-__all__ = ("validate_query_template",)
+__all__ = (
+    "PLACEHOLDER_NAMES",
+    "escape_non_placeholders",
+    "validate_query_template",
+)
+
+PLACEHOLDER_NAMES = frozenset({"labels", "window", "group_by"})
 
-_PLACEHOLDER_NAMES = frozenset({"labels", "window", "group_by"})
 _BRACE_BLOCK_RE = re.compile(r"\{([^{}]*)\}")
 _UNSUPPORTED_TEMPLATE_VAR_RE = re.compile(r"\$\{[^}]+\}|\$[A-Za-z_][A-Za-z0-9_]*")
 
 
-def _escape_non_placeholders(template: str) -> str:
+def escape_non_placeholders(template: str) -> str:
+    """Normalize each ``{X}`` so ``str.format`` produces a single PromQL ``{value}``
+    regardless of how many braces the user wrote.
+    """
+
     def repl(match: re.Match[str]) -> str:
         name = match.group(1)
         start, end = match.span()
         text = match.string
         already_wrapped = (
             start > 0 and text[start - 1] == "{" and end < len(text) and text[end] == "}"
         )
-        if name not in _PLACEHOLDER_NAMES:
+        if name not in PLACEHOLDER_NAMES:
             return match.group(0) if already_wrapped else "{{" + name + "}}"
         if name != "labels":
             return match.group(0)
@@ -36,13 +45,13 @@ def validate_query_template(template: str) -> str:
         raise InvalidMetricPresetTemplate("Template must not be empty.")
     unsupported_vars = _UNSUPPORTED_TEMPLATE_VAR_RE.findall(template)
     if unsupported_vars:
-        placeholders = ", ".join(f"{{{name}}}" for name in sorted(_PLACEHOLDER_NAMES))
+        placeholders = ", ".join(f"{{{name}}}" for name in sorted(PLACEHOLDER_NAMES))
         raise InvalidMetricPresetTemplate(
             f"Unsupported template variables: {unsupported_vars}. "
             f"Use placeholders {placeholders} or literal PromQL values."
         )
     try:
-        _escape_non_placeholders(template).format(labels="", window="", group_by="")
+        escape_non_placeholders(template).format(labels="", window="", group_by="")
     except (ValueError, KeyError, IndexError) as e:
         raise InvalidMetricPresetTemplate(
             f"Failed to render PromQL template ({type(e).__name__}: {e}): {template!r}"

src/ai/backend/manager/clients/prometheus/preset.py

@@ -1,33 +1,13 @@
-import re
 from collections.abc import Mapping, Set
 from dataclasses import dataclass, field
 from enum import StrEnum
 from typing import Self
 
+from ai.backend.common.dto.manager.v2.prometheus_query_preset.validators import (
+    escape_non_placeholders,
+)
 from ai.backend.common.exception import InvalidMetricPresetTemplate
 
-_PLACEHOLDER_NAMES = frozenset({"labels", "window", "group_by"})
-_BRACE_BLOCK_RE = re.compile(r"\{([^{}]*)\}")
-
-
-def _escape_non_placeholders(template: str) -> str:
-    # Normalize each `{X}` so str.format produces a single PromQL `{value}`
-    # regardless of how many braces the user wrote.
-    def repl(match: re.Match[str]) -> str:
-        name = match.group(1)
-        start, end = match.span()
-        text = match.string
-        already_wrapped = (
-            start > 0 and text[start - 1] == "{" and end < len(text) and text[end] == "}"
-        )
-        if name not in _PLACEHOLDER_NAMES:
-            return match.group(0) if already_wrapped else "{{" + name + "}}"
-        if name != "labels":
-            return match.group(0)
-        return match.group(0) if already_wrapped else "{{" + match.group(0) + "}}"
-
-    return _BRACE_BLOCK_RE.sub(repl, template)
-
 
 class LabelOperator(StrEnum):
     EQUAL = "="
@@ -80,7 +60,7 @@ def render(self) -> str:
             for key, value in self.labels.items()
         )
         try:
-            return _escape_non_placeholders(self.template).format(
+            return escape_non_placeholders(self.template).format(
                 labels=label_str,
                 window=self.window,
                 group_by=",".join(sorted(self.group_by)),