如何实际使用已安装的软件包版本，或找出为什么不可能？

Question

阴谋-新风格有一个习惯，偶尔安装，就像，所有依赖从零开始，没有明显的原因。对于使用lens和其他常见包的项目来说，这可能需要半小时以上的时间，尤其是当项目的目的只是为了快速编译一个仅在一个月前构建良好的可执行文件时。

阴谋集团确实提供了一种选择，指定作为约束，应该使用已经在全球安装的lens版本。然而，每当我尝试的时候，我只会

$ cabal new-run --constraint 'lens installed'
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: my-example-project-0.1.0.0 (user goal)
[__1] next goal: lens (dependency of dat103-Justus-lectures)
[__1] rejecting: lens-5.2, lens-5.1.1, lens-5.1, lens-5.0.1, lens-5,
lens-4.19.2, lens-4.19.1, lens-4.19, lens-4.18.1, lens-4.18, lens-4.17.1,
lens-4.17, lens-4.16.1, lens-4.16, lens-4.15.4, lens-4.15.3, lens-4.15.2,
lens-4.15.1, lens-4.15, lens-4.14, lens-4.13.2.1, lens-4.13.2, lens-4.13.1,
...
lens-0.4, lens-0.3, lens-0.2, lens-0.1 (constraint from command line flag
requires installed instance)
[__1] fail (backjumping, conflict set: my-example-project, lens)
After searching the rest of the dependency tree exhaustively

这是尽管有许多镜头版本可以在

$ ls -d ~/.cabal/store/ghc-8.6.4/lens*
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-1392f624ae052009275d5902a574e3f1804a66406a28222f0221cc2211da4f78
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-4854f213f63b67c0e1ea871303590def7a79bce4cc742f658e41dc4c76b56022
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-4caff99c8da3869df1dcfb67181d1be33d98316c3f458f93caedae05279c15e5
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-76531bf275303c15a9e6ae5160ca29f8fb15782d230b2576724103d67a4020d9
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-76a66d74e9cb85066009b345289db97d78bcf441beb12e6b762eb4d197000f19
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-813faecc9a5593fc14ef1677e82b9b384b66de9fff7843635cd7f4e5f4993d16
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-8c724c6d1fcc65ea38dc13fde30d86c4856151b235ef63628b23cee76d2feac5
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-90ec9224b09b828c948a6a1a310a085edc28f92a269bb839a2ac575dc60d579a
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-a157954a3d903fbf6444c054f9b704cab3fc23b36debc16fdc9ee8c0f5c0d5bd
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-c3bf086b6e081a91c7085b3c645652de0c4097edc4c88069203c5f741b14b97f
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-d5dca17dd7dddf6f324313f363ef74ff15d5717011dd750f415ce39942fc703b
/home/js/.cabal/store/ghc-8.6.4/lens-4.19.2-e4a1a8c9f3867cc6e6dc4dc059cc7fc0e4912d9aa4ce5476f63cdea9d3c8535e
/home/js/.cabal/store/ghc-8.6.4/lens-5.0.1-0956efd5ac393e6034c76c4dcc30a40ad1b12ad2b7a708e0f980648bac6287f3
/home/js/.cabal/store/ghc-8.6.4/lens-5.0.1-bfba2b0d59ebb884a2f32a960694c0e44af4fd29a21d8021ebdc42ce994fd055
/home/js/.cabal/store/ghc-8.6.4/lens-5.0.1-ce6c5a7496a674d60f93fae50caa4eb58acc26c6536937cce0f5243238cd6215
/home/js/.cabal/store/ghc-8.6.4/lens-5.0.1-d951ac24c700a8ae7f708a46a084e8fb4b0b008af29e5527f4d8986399248c62
/home/js/.cabal/store/ghc-8.6.4/lens-5.1-08384468083ebbc9d39619bfb59a32b97333acbf703c24bcf3b0bd22357a0115
...

那为什么不使用这些呢？如何找出Cabal甚至认为是“已安装的版本”，以及如何防止安装的版本停止使用？

Answer 1

正如注释中提到的，使用cabal freeze创建“冻结文件”是避免“更新搅动”的一种方法：

阴谋冻结写出一个冻结文件，该文件记录解决程序在当前索引和标志下选择的所有版本和标志。

如果您以前没有创建这样的文件，那么现在如何避免更新搅拌呢？cabal freeze似乎支持以下命令行选项：

 --index-state=STATE            Use source package index state as it existed
                                at a previous time. Accepts unix-timestamps
                                (e.g. '@1474732068'), ISO8601 UTC timestamps
                                (e.g. '2016-09-24T17:47:48Z'), or 'HEAD'
                                (default: 'HEAD').

因此，您可以提供大约一个月前的日期，希望可以生成冻结文件，而不考虑在该日期之后发布的项目依赖项的任何版本。