iOfficeAI/OfficeCLI · error · ArgumentException

Invalid path index '{indexStr}' in segment '{part}'. Expecte

Error message

Invalid path index '{indexStr}' in segment '{part}'. Expected a numeric index.

What it means

Thrown by the GenericXmlQuery path parser when the bracket content is neither a numeric index nor a recognized predicate. After extracting the text between '[' and ']', int.TryParse fails and IsContentFilterPath returns false, so the parser cannot interpret the segment as a position or a filter.

Source

Thrown at src/officecli/Core/GenericXmlQuery.cs:261

            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>
    public static OpenXmlElement? NavigateByPath(OpenXmlElement root, IReadOnlyList<(string Name, int? Index)> segments)
    {

View on GitHub (pinned to 1ced45e900)

Solutions

  1. Use a 1-based numeric index (e.g. row[2], not row[1.5] or row[abc]).
  2. If you meant a predicate, use recognized predicate syntax (e.g. @attr=value or a content filter) on the query/set/remove verbs.
  3. Check for typos or placeholder text inside the brackets.

Example fix

// before
Get(xml, "rows/row[two]"); // not numeric, not a predicate
// after
Get(xml, "rows/row[2]");
Defensive patterns

Strategy: validation

Validate before calling

static bool IsIndexSegment(string segment)
{
    var b = segment.IndexOf('[');
    if (b < 0) return true;
    var inner = segment[(b + 1)..^1];
    return int.TryParse(inner, out _);
}

Try / catch

try { Get(xml, path); }
catch (ArgumentException ex) when (ex.Message.Contains("Expected a numeric index"))
{ /* convert to numeric index or switch verb */ }

Prevention

When it happens

Trigger: Calling a path navigator with a segment like 'row[abc]' or 'slide[1.5]' — non-numeric, non-predicate bracket content that fails both int.TryParse and the predicate check.

Common situations: Typo in an index; attempting zero-based indexing (the parser expects 1-based); a malformed predicate not recognized by the filter detector; leftover placeholder text.

Related errors

AI-assisted analysis of iOfficeAI/OfficeCLI@1ced45e900 (2026-08-13). Data as JSON: /api/errors/e922f828be86e3ed. Report an issue: GitHub.