Error handling: Difference between revisions

(5 intermediate revisions by one other user not shown)

Line 8:

lib.warn "This is a sample warning message."

{

config.warnings = [

config.warnings = (

# Some NixOS module: throw error, if services.foo.bar == true

(lib.optionals config.services.foo.bar "This is also a sample warning message, but invoked differently.")

lib.optionals config.services.foo.bar "This is also a sample warning message, but invoked differently."

];

);

}

</syntaxHighlight>

Line 67:

~~As mentioned above~~, you can use <code>break</code> to debug nix code, <code>breakpointHook</code> to debug nix builds and interactive tools to debug NixOS tests.

To summarise debugging approaches discussed in this article, you can use <code>break</code> to debug nix code, <code>breakpointHook</code> to debug nix builds and interactive tools to debug NixOS tests.

To find the location where variables get defined, you can use the following tools:

For bare nix code, use <code>builtins.unsafeGetAttrPos

</code> ([https://github.com/NixOS/nix/blob/b17c4290cf61d8a0386817b87231762c175097c5/tests/lang/eval-okay-getattrpos.nix example]) which returns the line and column of where an attribute is defined. It is undocumented and considered bad practice.

(soon to come [https://github.com/NixOS/nixpkgs/pull/249243 github PR]): For NixOS options unsafeGetAttrPos doesn't work, but the module system itself records that information: to find the location of <code>config.networking.hostName</code>, use <code>:p options.networking.hostName.declarationPositions</code>.

== References ==

@@ Line 8: / Line 8: @@
 lib.warn "This is a sample warning message."
 {
-     config.warnings = [
+     config.warnings = (
        # Some NixOS module: throw error, if services.foo.bar == true
-       (lib.optionals config.services.foo.bar "This is also a sample warning message, but invoked differently.")
+       lib.optionals config.services.foo.bar "This is also a sample warning message, but invoked differently."
-     ];
+     );
 }
 </syntaxHighlight>
@@ Line 67: / Line 67: @@
 <!-- put debugging into a heading for search engine optimisation -->
-As mentioned above, you can use <code>break</code> to debug nix code, <code>breakpointHook</code> to debug nix builds and interactive tools to debug NixOS tests.
+To summarise debugging approaches discussed in this article, you can use <code>break</code> to debug nix code, <code>breakpointHook</code> to debug nix builds and interactive tools to debug NixOS tests.
+To find the location where variables get defined, you can use the following tools:
+For bare nix code, use <code>builtins.unsafeGetAttrPos
+</code> ([https://github.com/NixOS/nix/blob/b17c4290cf61d8a0386817b87231762c175097c5/tests/lang/eval-okay-getattrpos.nix example]) which returns the line and column of where an attribute is defined. It is undocumented and considered bad practice.
+(soon to come [https://github.com/NixOS/nixpkgs/pull/249243 github PR]): For NixOS options unsafeGetAttrPos doesn't work, but the module system itself records that information: to find the location of <code>config.networking.hostName</code>, use <code>:p options.networking.hostName.declarationPositions</code>.
 == References ==