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
This commit is contained in:
parent
d00edfb28d
commit
14bf54bd39
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@ -1,20 +1,18 @@
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---
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synopsis: "Trace when the `foo` part of a `foo.bar.baz` expression errors"
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cls: 1505
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synopsis: "Trace which part of a `foo.bar.baz` expression errors"
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cls: 1505, 1506
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credits: Qyriad
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category: Improvements
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---
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Previously, if an expression like `linux_4_9.meta.description` errored in the `linux_4_9` part, it wouldn't show you that that's the part of the expression that failed to evaluate, or even that that line of code is what caused evaluation of the failing expression.
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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.
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The previous error looks like this:
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```
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let
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inherit (pkgs.linuxKernel.kernels) linux_4_9;
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in linux_4_9.meta.description
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pkgs.linuxKernel.kernels.linux_4_9.meta.description
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error:
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… while evaluating the attribute 'linux_4_9'
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… while evaluating the attribute 'linuxKernel.kernels.linux_4_9.meta.description'
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at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:5:
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277| } // lib.optionalAttrs config.allowAliases {
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278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
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@ -33,6 +31,36 @@ error:
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Now, the error will look like this:
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```
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pkgs.linuxKernel.kernels.linux_4_9.meta.description
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error:
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… while evaluating the attribute 'linuxKernel.kernels.linux_4_9.meta.description'
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at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:5:
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277| } // lib.optionalAttrs config.allowAliases {
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278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
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| ^
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279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
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… while evaluating 'pkgs.linuxKernel.kernels.linux_4_9' to select 'meta' on it
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at «string»:1:1:
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1| pkgs.linuxKernel.kernels.linux_4_9.meta.description
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| ^
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… caused by explicit throw
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at /nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source/pkgs/top-level/linux-kernels.nix:278:17:
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277| } // lib.optionalAttrs config.allowAliases {
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278| linux_4_9 = throw "linux 4.9 was removed because it will reach its end of life within 22.11";
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| ^
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279| linux_4_14 = throw "linux 4.14 was removed because it will reach its end of life within 23.11";
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error: linux 4.9 was removed because it will reach its end of life within 22.11
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```
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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.
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This includes if the failing part is a top-level binding:
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```
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let
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inherit (pkgs.linuxKernel.kernels) linux_4_9;
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@ -60,5 +88,3 @@ error:
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error: linux 4.9 was removed because it will reach its end of life within 22.11
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```
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Not only does the line of code that referenced the failing binding show up in the trace, it also tells you that it was specifically the `linux_4_9` part that failed.
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@ -1458,12 +1458,46 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
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showAttrPath(state, env, attrPath))
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: nullptr;
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for (auto const & currentAttrName : attrPath) {
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for (auto const & [partIdx, currentAttrName] : enumerate(attrPath)) {
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state.nrLookups++;
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Symbol const name = getName(currentAttrName, state, env);
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state.forceValue(*vCurrent, pos);
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// For formatting errors, which should be done only when needed.
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auto partsSoFar = [&]() -> std::string {
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std::stringstream ss;
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// We start with the base thing this ExprSelect is selecting on.
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assert(this->e != nullptr);
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this->e->show(state.symbols, ss);
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// Then grab each part of the attr path up to this one.
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assert(partIdx < attrPath.size());
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std::span<AttrName> const parts(
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attrPath.begin(),
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attrPath.begin() + partIdx
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);
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// And convert them to strings and join them.
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for (auto const & part : parts) {
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auto const partName = getName(part, state, env);
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ss << "." << state.symbols[partName];
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}
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return ss.str();
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};
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try {
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state.forceValue(*vCurrent, pos);
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} catch (Error & e) {
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state.addErrorTrace(
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e,
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getPos(),
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"while evaluating '%s' to select '%s' on it",
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partsSoFar(),
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state.symbols[name]
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);
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throw;
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}
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if (vCurrent->type() != nAttrs) {
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@ -1479,7 +1513,10 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
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"expected a set but found %s: %s",
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showType(*vCurrent),
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ValuePrinter(state, *vCurrent, errorPrintOptions)
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).withTrace(pos, "while selecting an attribute").debugThrow();
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).addTrace(
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pos,
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HintFmt("while selecting '%s' on '%s'", state.symbols[name], partsSoFar())
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).debugThrow();
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}
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// Now that we know this is actually an attrset, try to find an attr
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