NixOS/nix

[FEAT]: Introduce new error message for packages without `mainProgram`

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#15,138 建立於 2026年2月3日

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描述

Is your feature request related to a problem?

Some packages have multiple binaries with different purposes therefore setting mainProgram is not desirable.

When mainProgram is not set for these packages nix run errors out with

error: unable to execute '/nix/store/abc/bin/xyz': No such file or directory

Proposed solution

A new error for packages that don't have the mainProgram attribute set, something like

error: in 'abc': 'mainProgram' isn't set

Alternative solutions

An option to set mainProgram to null for packages that desire to do so, leaving the default behavior of mainProgram = pname; intact. An error like

error: 'abc' doesn't have a default binary

would be better in this case.

Additional context

https://github.com/NixOS/nixpkgs/issues/486543

Checklist

Add :+1: to issues you find important.

貢獻者指南

技術棧
cpp
領域
cli
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
mostly clear
前置要求
Basic understanding of NixFamiliarity with Nix error handling
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
60
研究方向
Investigate where the error 'unable to execute ... No such file or directory' is produced (likely in src/libstore or src/libexpr). Look for how mainProgram is handled in drv evaluation. The goal is to add a check before that error is thrown when mainProgram is not set, emitting a clearer message like 'mainProgram isn't set'. Refer to the linked issue https://github.com/NixOS/nixpkgs/issues/486543 for context. The implementation may involve modifying the Nix expression evaluator or the build execution code path.