iOfficeAI/OfficeCLI · error · ArgumentException

'{part}' is a predicate, but this verb navigates by position

Error message

'{part}' is a predicate, but this verb navigates by position and expects a numeric index (e.g. {part[..part.IndexOf('[')]}[2]). Predicates work on 'query' (read) and 'set'/'remove' (mutate matched elements).

What it means

Thrown by the GenericXmlQuery path parser when the bracket content is a predicate (content filter) rather than a numeric index, but the verb in use navigates by position only. 'get' is one-node-by-path by contract; predicates run on the selector engine used by 'query' (read) and 'set'/'remove' (mutate). The message directs the caller to the verbs that support predicates.

Source

Thrown at src/officecli/Core/GenericXmlQuery.cs:259

        {
            if (string.IsNullOrEmpty(part)) continue;
            var bracketIdx = part.IndexOf('[');
            if (bracketIdx >= 0)
            {
                // BUG-R36-01 fix: when ']' is missing (e.g. "slide[") the expression
                // part[(bracketIdx+1)..^1] produces a negative-length range crash.
                // Detect and reject unclosed brackets with a clean ArgumentException.
                var closingIdx = part.IndexOf(']', bracketIdx + 1);
                if (closingIdx < 0)
                    throw new ArgumentException($"Malformed path segment '{part}'. Bracket '[' is not closed. Expected format: name[index] or name[@attr=value].");
                var name = PathAliases.Resolve(part[..bracketIdx]);
                var indexStr = part[(bracketIdx + 1)..^1];
                if (!int.TryParse(indexStr, out var idx))
                    // A predicate in the index slot (row[Score>0], row[not(V)])
                    // means the caller reached the single-node path navigator
                    // with a FILTER. get is one-node-by-path by contract;
                    // point at the verbs that run the selector engine.
                    throw new ArgumentException(AttributeFilter.IsContentFilterPath($"[{indexStr}]")
                        ? $"'{part}' is a predicate, but this verb navigates by position and expects a numeric index (e.g. {part[..part.IndexOf('[')]}[2]). Predicates work on 'query' (read) and 'set'/'remove' (mutate matched elements)."
                        : $"Invalid path index '{indexStr}' in segment '{part}'. Expected a numeric index.");
                if (idx < 1)
                    throw new ArgumentException($"Invalid path index '{idx}' in segment '{part}'. Index must be >= 1.");
                segments.Add((name, idx));
            }
            else
            {
                segments.Add((PathAliases.Resolve(part), null));
            }
        }
        return segments;
    }

    /// <summary>
    /// Navigate an OpenXML element tree by path segments (localName + optional 1-based index).
    /// Returns null if any segment cannot be resolved.
    /// </summary>

View on GitHub (pinned to 1ced45e900)

Solutions

  1. Switch to the 'query' verb for read filtering, or 'set'/'remove' for mutating matched elements.
  2. For positional navigation with get, use a numeric index (e.g. row[2]).
  3. Confirm whether you need a single node (get) or a filtered set (query).

Example fix

// before
Get(xml, "rows/row[Score>0]"); // get cannot predicate
// after
Query(xml, "rows/row[Score>0]"); // query runs the selector engine
Defensive patterns

Strategy: validation

Validate before calling

static string ChooseVerbForSegment(string segment) =>
    segment.Contains('[') && AttributeFilter.IsContentFilterPath(segment[segment.IndexOf('[')..])
        ? "query" : "get";

Prevention

When it happens

Trigger: Calling get with a segment like 'row[Score>0]' or 'row[not(V)]' where the bracket content is recognized by AttributeFilter.IsContentFilterPath as a predicate rather than a number.

Common situations: Using get expecting it to filter; confusing positional navigation (row[2]) with predicate filtering (row[Score>0]); porting a query-style path to the get verb.

Related errors

AI-assisted analysis of iOfficeAI/OfficeCLI@1ced45e900 (2026-08-13). Data as JSON: /api/errors/00661ad8edc51797. Report an issue: GitHub.