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CompletionSources not sorted properly when building HelpName default suggestions

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@zjdangge 已经在做这个了。

开始于 2026年10月15日。

  • #2858 来自 @zjdangge —— 未关闭

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csharp
领域
cli

调研方向

从 src/command-line-api/src/System.CommandLine/Option.cs 第 142 行开始，使用 issue 中的 CompletionItem 示例复现该顺序。跟踪空的和部分填写的 CompletionContext 值如何参与排序，然后验证帮助建议和 Tab 补全遵循 issue 中显示的顺序。

由索引模型根据 Issue 内容生成。

描述

The sorting logic done here when building the default help text from the list of completions is backward:

https://github.com/dotnet/dotnet/blob/2db1f5ee2bdda2e8d873769325fabede32e420e0/src/command-line-api/src/System.CommandLine/Option.cs#L142

Since the ThenBy is on the Label, the resulting sorted collection is re-sorted by Label, as a primary order, not as a secondary order like SQL.

And, to hoist the current entry to the top of the list, the OrderBy needs to be OrderByDescending.

Here is an example that shows the bad behavior:


public static class Program
{
    static CompletionItem[] sampleCompletions =
    [
      new ( "5", sortText: "05" ),
      new ( "10", sortText: "10" ),
      new ( "6", sortText: "06" ),
      new ( "20", sortText: "10" ),
      new ( "30", sortText: "30" )
    ];

    public static async Task<int> Main ( string[] argv)
    {
    RootCommand root   = new ( "example" );
    Option<int> option = new ( "option" );
    option.CompletionSources.Add ( static ctx => sampleCompletions );
    root.Options.Add ( option );
    await root.Parse ( [ "--help" ] ).InvokeAsync ( );
    }
}

Output:
```text
Description:
  example

Usage:
  SnapsInAZfs [options]

Options:
  option <10|20|30|5|6>
  -?, -h, --help         Show help and usage information
  --version              Show version information

Note the improperly ordered suggestions in the HelpName for option.

Here is why, isolated to what the line referenced at the top of the issue does:

      CompletionContext theCompletionContext = CompletionContext.Empty;
      IOrderedEnumerable<CompletionItem> improperlyOrdered = sampleCompletions
                                                            .OrderBy ( item => item.SortText.IndexOfCaseInsensitive ( theCompletionContext.WordToComplete ) )
                                                            .ThenBy ( item => item. Label, StringComparer.OrdinalIgnoreCase );

      foreach ( CompletionItem c in improperlyOrdered )
      {
        Console.WriteLine ( c.Label );
      }

Output:

10
20
30
5
6

Here is the fixed sorting code, as it applies to building HelpText (an empty context gets passed in):

    IOrderedEnumerable<CompletionItem> properlyOrdered = sampleCompletions
                                                        .OrderByDescending ( item => item.Label.IndexOfCaseInsensitive ( theCompletionContext.WordToComplete ) )
                                                        .ThenBy ( item => item.SortText, StringComparer.OrdinalIgnoreCase );

    foreach ( CompletionItem c in properlyOrdered )
    {
      Console.WriteLine ( c.Label );
    }

Output:

5
6
10
20
30

And here is how it would look during tab completion, if the user had already entered "2" and then presses tab (simulated by giving it the "2" directly):

    IOrderedEnumerable<CompletionItem> properlyOrderedWithPartialEntry = sampleCompletions
                                                                        .OrderByDescending ( item => item.Label.IndexOfCaseInsensitive ( "2" ) )
                                                                        .ThenBy ( item => item.SortText, StringComparer.OrdinalIgnoreCase );

    foreach ( CompletionItem c in properlyOrderedWithPartialEntry )
    {
      Console.WriteLine ( c.Label );
    }

Output:

20
5
6
10
30

The actual code to replace what is there now would be:
This is incorrect. See my follow-up comment that fixes it.

            return completions
                   .OrderByDescending(item => item.Label.IndexOfCaseInsensitive(context.WordToComplete))
                   .ThenBy(symbol => symbol.SortText, StringComparer.OrdinalIgnoreCase);

Also, it may be worth pointing out that the extension method IndexOfCaseInsensitive does not use the same StringComparer as the code here. It uses invariant culture. This uses ordinal. So the two sorts aren't the same, necessarily, even if the values are identical.

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