fix: fail loudly on an unknown workflow expression filter (#3074)

* fix: fail loudly on an unknown workflow expression filter

The expression evaluator's filter dispatch fell through to `return value`
for any unregistered filter, so a typo'd or unsupported filter such as
`{{ items | length }}` rendered the value unchanged with no error and the
run completed — a silent wrong result.

Raise a clear ValueError instead, naming the offending filter and the valid
ones, mirroring the strict handling already used for `from_json`. The five
registered filters (default/join/map/contains/from_json) are unchanged; the
`name(arg)` form of an unknown filter is now caught too.

* fix: distinguish a misused registered filter from an unknown one; cover map

Address the review feedback on the unknown-filter fail-loud path:

- A *registered* filter used in an unsupported form (e.g. `| join` or
  `| map` with no argument) raised the misleading "unknown filter
  '<name>'" — the filter is registered, the syntax isn't. It now raises
  a message naming it as a known filter misused. A new
  `_REGISTERED_FILTERS` constant drives the distinction.
- `test_registered_filters_unaffected` now also exercises `map('attr')`,
  which it previously claimed to cover but didn't. Add
  `test_registered_filter_unsupported_form_raises` to pin the new path.

* fix: include the no-arg default form in the filter-error hint

Copilot review: the hint listed default('x') but omitted the valid
no-argument default form (| default), which this module supports.

src/specify_cli/workflows/expressions.py

@@ -12,6 +12,19 @@ import re
 from typing import Any
 
 
+# The filters the expression evaluator recognizes. Used to tell a
+# *registered* filter used in an unsupported form (e.g. `| join` with no
+# argument) apart from a genuinely unknown filter name, so each raises an
+# error that names the real problem.
+_REGISTERED_FILTERS: tuple[str, ...] = (
+    "default",
+    "join",
+    "map",
+    "contains",
+    "from_json",
+)
+
+
 # -- Custom filters -------------------------------------------------------
 
 def _filter_default(value: Any, default_value: Any = "") -> Any:
@@ -192,7 +205,27 @@ def _evaluate_simple_expression(expr: str, namespace: dict[str, Any]) -> Any:
         filter_name = filter_expr.strip()
         if filter_name == "default":
             return _filter_default(value)
-        return value
+        # No recognized filter matched. Fail loudly rather than silently
+        # returning the unfiltered value: a passthrough turns a mis-typed or
+        # unsupported filter into a wrong result with no signal. Mirrors the
+        # strict `from_json` handling above. Distinguish a *registered* filter
+        # used in an unsupported form (e.g. `| join` or `| map` with no
+        # argument) from a genuinely unknown filter name, so the message names
+        # the real problem instead of calling a known filter "unknown".
+        leading_name = re.match(r"\w+", filter_expr)
+        name = leading_name.group(0) if leading_name else filter_expr
+        expected = (
+            "expected one of default or default('x'), join('sep'), "
+            "map('attr'), contains('s'), or from_json"
+        )
+        if name in _REGISTERED_FILTERS:
+            raise ValueError(
+                f"filter '{name}' used in an unsupported form (got "
+                f"'| {filter_expr}'): {expected}"
+            )
+        raise ValueError(
+            f"unknown filter '{name}': {expected} (got '| {filter_expr}')"
+        )
 
     # Boolean operators — parse 'or' first (lower precedence) so that
     # 'a or b and c' is evaluated as 'a or (b and c)'.