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toJSON: report error position for fancier output

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Given flake:

```nix
{ description = "nix json error provenance";
  inputs = {};
  outputs = { self }: {
    jsonFunction = _: "function";
    json = builtins.toJSON (_: "function");
  };
}

```
- Before:

```console
❯ nix eval --json .#jsonFunction
error: cannot convert a function to JSON
```

- After:

```console
❯ nix eval --json .#jsonFunction
error: cannot convert a function to JSON

       at /nix/store/b7imf1c2j4jnkg3ys7fsfbj02s5j0i4f-source/testflake/flake.nix:4:5:

            3|   outputs = { self }: {
            4|     jsonFunction = _: "function";
             |     ^
            5|     json = builtins.toJSON (_: "function");
```
This commit is contained in:
Shay Bergmann 2021-10-25 21:13:35 +00:00
parent 4a2b7cc68c
commit ba81e871b2
No known key found for this signature in database
GPG key ID: 4D33B73FFDB9217C
6 changed files with 22 additions and 16 deletions
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24
src/libexpr/value-to-json.cc
View file

@ -10,11 +10,11 @@
namespace nix {
void printValueAsJSON(EvalState & state, bool strict,
Value & v, JSONPlaceholder & out, PathSet & context)
Value & v, const Pos & pos, JSONPlaceholder & out, PathSet & context)
{
checkInterrupt();
if (strict) state.forceValue(v);
if (strict) state.forceValue(v, pos);
switch (v.type()) {
@ -54,10 +54,10 @@ void printValueAsJSON(EvalState & state, bool strict,
for (auto & j : names) {
Attr & a(*v.attrs->find(state.symbols.create(j)));
auto placeholder(obj.placeholder(j));
printValueAsJSON(state, strict, *a.value, placeholder, context);
printValueAsJSON(state, strict, *a.value, *a.pos, placeholder, context);
}
} else
printValueAsJSON(state, strict, *i->value, out, context);
printValueAsJSON(state, strict, *i->value, *i->pos, out, context);
break;
}
@ -65,7 +65,7 @@ void printValueAsJSON(EvalState & state, bool strict,
auto list(out.list());
for (unsigned int n = 0; n < v.listSize(); ++n) {
auto placeholder(list.placeholder());
printValueAsJSON(state, strict, *v.listElems()[n], placeholder, context);
printValueAsJSON(state, strict, *v.listElems()[n], noPos, placeholder, context);
}
break;
}
@ -79,18 +79,24 @@ void printValueAsJSON(EvalState & state, bool strict,
break;
case nThunk:
throw TypeError("cannot convert %1% to JSON", showType(v));
throw TypeError({
.msg = hintfmt("cannot convert %1% to JSON", showType(v)),
.errPos = pos
});
case nFunction:
throw TypeError("cannot convert %1% to JSON", showType(v));
throw TypeError({
.msg = hintfmt("cannot convert %1% to JSON", showType(v)),
.errPos = pos
});
}
}
void printValueAsJSON(EvalState & state, bool strict,
Value & v, std::ostream & str, PathSet & context)
Value & v, const Pos & pos, std::ostream & str, PathSet & context)
{
JSONPlaceholder out(str);
printValueAsJSON(state, strict, v, out, context);
printValueAsJSON(state, strict, v, pos, out, context);
}
void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,