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Print top-level errors normally in nix repl

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Previously, errors while printing values in `nix repl` would be printed
in `«error: ...»` brackets rather than displayed normally:

```
nix-repl> legacyPackages.aarch64-darwin.pythonPackages.APScheduler
«error: Package ‘python-2.7.18.7’ in /nix/store/6s0m1qc31zw3l3kq0q4wd5cp3lqpkq0q-source/pkgs/development/interpreters/python/cpython/2.7/default.nix:335 is marked as insecure, refusing to evaluate.»
```

Now, errors will be displayed normally if they're emitted at the
top-level of an expression:

```
nix-repl> legacyPackages.aarch64-darwin.pythonPackages.APScheduler
error:
       … in the condition of the assert statement
         at /nix/store/6s0m1qc31zw3l3kq0q4wd5cp3lqpkq0q-source/lib/customisation.nix:268:17:
          267|     in commonAttrs // {
          268|       drvPath = assert condition; drv.drvPath;
             |                 ^
          269|       outPath = assert condition; drv.outPath;

       … in the left operand of the OR (||) operator
         at /nix/store/6s0m1qc31zw3l3kq0q4wd5cp3lqpkq0q-source/pkgs/development/interpreters/python/passthrufun.nix:28:45:
           27|         if lib.isDerivation value then
           28|           lib.extendDerivation (valid value || throw "${name} should use `buildPythonPackage` or `toPythonModule` if it is to be part of the Python packages set.") {} value
             |                                             ^
           29|         else

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: Package ‘python-2.7.18.7’ in /nix/store/6s0m1qc31zw3l3kq0q4wd5cp3lqpkq0q-source/pkgs/development/interpreters/python/cpython/2.7/default.nix:335 is marked as insecure, refusing to evaluate.
```

Errors emitted in nested structures (like e.g. when printing `nixpkgs`)
will still be printed in brackets.
This commit is contained in:
Rebecca Turner 2024-03-09 18:28:04 -08:00
parent ac730622e8
commit d13c63afa2
No known key found for this signature in database
3 changed files with 91 additions and 62 deletions
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30
src/libexpr/print-options.hh
View file

@ -8,6 +8,29 @@
namespace nix {
/**
* How errors should be handled when printing values.
*/
enum class ErrorPrintBehavior {
/**
* Print the first line of the error in brackets: `«error: oh no!»`
*/
Print,
/**
* Throw the error to the code that attempted to print the value, instead
* of suppressing it it.
*/
Throw,
/**
* Only throw the error if encountered at the top level of the expression.
*
* This will cause expressions like `builtins.throw "uh oh!"` to throw
* errors, but will print attribute sets and other nested structures
* containing values that error (like `nixpkgs`) normally.
*/
ThrowTopLevel,
};
/**
* Options for printing Nix values.
*/
@ -68,6 +91,11 @@ struct PrintOptions
*/
size_t prettyIndent = 0;
/**
* How to handle errors encountered while printing values.
*/
ErrorPrintBehavior errors = ErrorPrintBehavior::Print;
/**
* True if pretty-printing is enabled.
*/
@ -86,7 +114,7 @@ static PrintOptions errorPrintOptions = PrintOptions {
.maxDepth = 10,
.maxAttrs = 10,
.maxListItems = 10,
.maxStringLength = 1024
.maxStringLength = 1024,
};
}