[Nix-dev] string vs path hell

[Kirill Elagin]

Going further:

~~~~~~~~~~~
nix-repl> a = "${pkgs.busybox}/foo/bar"

nix-repl> b =
"/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar"

nix-repl> a
"/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar"

nix-repl> b
"/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar"

nix-repl> lib.substring 0 1 a
"/"

nix-repl> lib.substring 0 1 b
"/"

nix-repl> lib.substring 0 1 a == "/"
false

nix-repl> lib.substring 0 1 b == "/"
true
~~~~~~~~~~~~~


--
Кирилл Елагин


On Tue, Jun 10, 2014 at 1:04 PM, Kirill Elagin <kirelagin at gmail.com> wrote:

> Oh yeah, I've managed to reproduce this:
>
> ~~~~~
> nix-repl> :l <nixpkgs>
> Added 3863 variables.
>
> nix-repl> lib.splitString "/" "${pkgs.busybox}/foo/bar"
> [ "/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar" ]
>
> nix-repl> lib.splitString "/" (toString "${pkgs.busybox}/foo/bar")
> [ "/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar" ]
>
> nix-repl> lib.splitString "/"
> "/nix/store/nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1/foo/bar"
> [ "" "nix" "store" "nn00kn1fa0154qa1szszijw825cha8ps-busybox-1.22.1" "foo"
> "bar" ]
> ~~~~~
>
> Total weirdness.
>
>
> --
> Кирилл Елагин
>
>
> On Tue, Jun 10, 2014 at 12:58 PM, Kirill Elagin <kirelagin at gmail.com>
> wrote:
>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> let lib = (import <nixpkgs> {}).lib;
>>     exe = {
>>       foo = "/some/path/to/foo";
>>       bar = "/other/path/to/bar";
>>     };
>> in
>> {
>>   contents =
>>
>>     map (v :
>>       let
>>         takeFileName = p :
>>           let fl = lib.splitString "/" p; in lib.last fl;
>>         fn = takeFileName "${v}";
>>         dummy = takeFileName "/a/string/encoded/path/dummy";
>>       in
>>
>>         #builtins.trace fn
>>         #builtins.trace dummy
>>
>>
>>         {
>>           symlink = "/bin/${fn}";
>>           object = v;
>>         }) (lib.attrValues exe);
>> }
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> ~~~~~~~~~~~~~~~~
>> nix-repl> :l test.nix
>> Added 1 variables.
>>
>> nix-repl> :p contents
>> [ { object = "/other/path/to/bar"; symlink = "/bin/bar"; } { object =
>> "/some/path/to/foo"; symlink = "/bin/foo"; } ]
>> ~~~~~~~~~~~~~~~~~
>>
>> Dunno, you should probably inspect your `exe` set closer in case
>> something's wrong with values there.
>>
>>
>> --
>> Кирилл Елагин
>>
>>
>> On Tue, Jun 10, 2014 at 10:41 AM, Sergey Mironov <grrwlf at gmail.com>
>> wrote:
>>
>>> OK, you are right. My code snippet really works fine. So I feel I must
>>> post a part of my real code which still doesn't work for me. It is a
>>> bit long, but maybe you will be able to help me find a mistake. Here
>>> it is (below). This expression takes a set of paths to the executables
>>> (exe // setuids) and builds the initrd image. Every attribute of (exe
>>> // setuids) is either a string like [adduser =
>>> "${busybox}/sbin/adduser";] or the result of mkDerivation producing
>>> the single binary in it's $out.
>>>
>>> Note the "dummy" expression. If I uncomment "builtins.trace dummy"
>>> line, it will show me the expected result (string "dummy" for every
>>> list item). But in the same time, "builtins.trace fn" shows that fn is
>>> evaluated incorrectly. Every time it contains full Nix path
>>> ("/nix/strote/...", see example at the end of the letter) instead of
>>> the filename part. It looks like 'splitString' doesn't recognize it's
>>> argument as a string.
>>>
>>> Please, comment!
>>> Sergey
>>>
>>>
>>> --
>>> the code
>>>
>>>       ...
>>>
>>>       img = makeInitrd {
>>>
>>>         compressor = "${gzip}/bin/gzip --fast";
>>>
>>>         contents = with all.ipkgs;
>>>           [{ symlink = "/init";
>>>             object = exe.init;
>>>           }
>>>           { symlink = "/bin/sh";
>>>             object = exe.shell;
>>>           }] ++
>>>           map (v :
>>>
>>>             let
>>>
>>>               takeFileName = p : let
>>>                   fl = lib.splitString "/" p;
>>>                 in lib.last fl;
>>>
>>>               fn = takeFileName "${v}";
>>>
>>>               dummy = takeFileName "/a/string/encoded/path/dummy";
>>>
>>>             in
>>>
>>>             # builtins.trace fn   # <---------------- see example output
>>> below
>>>             # builtins.trace dummy
>>>
>>>             {
>>>               symlink = "/bin/${fn}";
>>>               object = v;
>>>             }) (lib.attrValues (exe // setuids));
>>>       };
>>>
>>> --
>>> example output of "builtins.trace fn":
>>>
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/sbin/addgroup
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/sbin/adduser
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/false
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/true
>>> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/awk
>>> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/cat
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/chmod
>>> trace:
>>> /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/chown
>>> trace: /nix/store/sx19dvnv3wi2j8pvyra8npl9vdwdbmrk-busybox-1.21.1/bin/cp
>>> trace:
>>> /nix/store/h8rs91fjivsh6wakmwmpkca31wfp38g0-msr-tools-1.3/bin/cpuid
>>>
>>
>>
>
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