lix/doc/manual/rl-next/better-attrpath-errors.md

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---
trace which part of `foo.bar.baz` errors Turns errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar into errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while evaluating 'somepkg.src' to select 'meta' on it at «string»:3:4: 2| somepkg.src = throw "invalid foobar"; 3| in somepkg.src.meta | ^ … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar And for type errors, from: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting an attribute at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" into: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting 'meta' on 'somepkg.src' at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" For the low price of an enumerate() and a lambda you too can have the incorrect line of code actually show up in the trace! Change-Id: Ic1491c86e33c167891bdac9adad6224784760bd6
2024-06-23 03:59:47 +00:00
synopsis: "Trace which part of a `foo.bar.baz` expression errors"
cls: 1505, 1506
credits: Qyriad
category: Improvements
---
trace which part of `foo.bar.baz` errors Turns errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar into errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while evaluating 'somepkg.src' to select 'meta' on it at «string»:3:4: 2| somepkg.src = throw "invalid foobar"; 3| in somepkg.src.meta | ^ … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar And for type errors, from: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting an attribute at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" into: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting 'meta' on 'somepkg.src' at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" For the low price of an enumerate() and a lambda you too can have the incorrect line of code actually show up in the trace! Change-Id: Ic1491c86e33c167891bdac9adad6224784760bd6
2024-06-23 03:59:47 +00:00
Previously, if an attribute path selection expression like `linux_4_9.meta.description` it wouldn't show you which one of those parts in the attribute path, or even that that line of code is what caused evaluation of the failing expression.
The previous error looks like this:
```
trace which part of `foo.bar.baz` errors Turns errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar into errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while evaluating 'somepkg.src' to select 'meta' on it at «string»:3:4: 2| somepkg.src = throw "invalid foobar"; 3| in somepkg.src.meta | ^ … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar And for type errors, from: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting an attribute at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" into: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting 'meta' on 'somepkg.src' at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" For the low price of an enumerate() and a lambda you too can have the incorrect line of code actually show up in the trace! Change-Id: Ic1491c86e33c167891bdac9adad6224784760bd6
2024-06-23 03:59:47 +00:00
pkgs.linuxKernel.kernels.linux_4_9.meta.description
error:
trace which part of `foo.bar.baz` errors Turns errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar into errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while evaluating 'somepkg.src' to select 'meta' on it at «string»:3:4: 2| somepkg.src = throw "invalid foobar"; 3| in somepkg.src.meta | ^ … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar And for type errors, from: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting an attribute at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" into: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting 'meta' on 'somepkg.src' at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" For the low price of an enumerate() and a lambda you too can have the incorrect line of code actually show up in the trace! Change-Id: Ic1491c86e33c167891bdac9adad6224784760bd6
2024-06-23 03:59:47 +00:00
… while evaluating the attribute 'linuxKernel.kernels.linux_4_9.meta.description'
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:5:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
… while calling the 'throw' builtin
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:17:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
error: linux 4.9 was removed because it will reach its end of life within 22.11
```
Now, the error will look like this:
trace which part of `foo.bar.baz` errors Turns errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar into errors like: let somepkg.src = throw "invalid foobar"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta … while evaluating 'somepkg.src' to select 'meta' on it at «string»:3:4: 2| somepkg.src = throw "invalid foobar"; 3| in somepkg.src.meta | ^ … while calling the 'throw' builtin at «string»:2:17: 1| let 2| somepkg.src = throw "invalid foobar"; | ^ 3| in somepkg.src.meta error: invalid foobar And for type errors, from: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting an attribute at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" into: let somepkg.src = "I'm not an attrset"; in somepkg.src.meta error: … while evaluating the attribute 'src.meta' at «string»:2:3: 1| let 2| somepkg.src = "I'm not an attrset"; | ^ 3| in somepkg.src.meta … while selecting 'meta' on 'somepkg.src' at «string»:3:4: 2| somepkg.src = "I'm not an attrset"; 3| in somepkg.src.meta | ^ error: expected a set but found a string: "I'm not an attrset" For the low price of an enumerate() and a lambda you too can have the incorrect line of code actually show up in the trace! Change-Id: Ic1491c86e33c167891bdac9adad6224784760bd6
2024-06-23 03:59:47 +00:00
```
pkgs.linuxKernel.kernels.linux_4_9.meta.description
error:
… while evaluating the attribute 'linuxKernel.kernels.linux_4_9.meta.description'
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:5:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
… while evaluating 'pkgs.linuxKernel.kernels.linux_4_9' to select 'meta' on it
at «string»:1:1:
1| pkgs.linuxKernel.kernels.linux_4_9.meta.description
| ^
… caused by explicit throw
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:17:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
error: linux 4.9 was removed because it will reach its end of life within 22.11
```
Not only does the line of code that referenced the failing attribute show up in the trace, it also tells you that it was specifically the `linux_4_9` part that failed.
This includes if the failing part is a top-level binding:
```
let
inherit (pkgs.linuxKernel.kernels) linux_4_9;
in linux_4_9.meta.description
error:
… while evaluating 'linux_4_9' to select 'meta.description' on it
at «string»:3:4:
2| inherit (pkgs.linuxKernel.kernels) linux_4_9;
3| in linux_4_9.meta.description
| ^
… while evaluating the attribute 'linux_4_9'
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:5:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
… caused by explicit throw
at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:17:
277| } // lib.optionalAttrs config.allowAliases {
278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
| ^
279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
error: linux 4.9 was removed because it will reach its end of life within 22.11
```