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Bad diagnostic for interpolating null into a string #665

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opened 2025-02-10 23:56:58 +00:00 by jade · 0 comments
jade commented 2025-02-10 23:56:58 +00:00
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$ nix build -L --expr 'builtins.derivation { jacked = "${null}"; system = "aarch64-darwin"; name = "foo6"; builder = "/bin/sh"; args = ["-c" "> $out"]; }'                          
error:
       … while evaluating an expression to select 'drvPath' on it
         at «internal»:1:552:
       … while calling the 'derivationStrict' builtin
         at «internal»:1:208:
       (stack trace truncated; use '--show-trace' to show the full trace)

       error: cannot coerce null to a string: null

Without being jade and having seen this 1000 times and knowing that "coerce to a string" means "${...}", it is really hard to know what is actually broken. The message needs some copy editing to actually say what was being done there: it should say something about interpolating into a string. This error message also has a side of #239 and #664, since the stack trace is worthless.

``` $ nix build -L --expr 'builtins.derivation { jacked = "${null}"; system = "aarch64-darwin"; name = "foo6"; builder = "/bin/sh"; args = ["-c" "> $out"]; }' error: … while evaluating an expression to select 'drvPath' on it at «internal»:1:552: … while calling the 'derivationStrict' builtin at «internal»:1:208: (stack trace truncated; use '--show-trace' to show the full trace) error: cannot coerce null to a string: null ``` Without being jade and having seen this 1000 times and knowing that "coerce to a string" means "${...}", it is really hard to know what is actually broken. The message needs some copy editing to actually say what was being done there: it should say something about *interpolating* into a string. This error message also has a side of https://git.lix.systems/lix-project/lix/issues/239 and https://git.lix.systems/lix-project/lix/issues/664, since the stack trace is worthless.
jade added this to the Error reporting project 2025-02-10 23:56:58 +00:00
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Reference: lix-project/lix#665
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