Error handling: Difference between revisions

(3 intermediate revisions by 2 users 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 19:

The nix language has a construct to help with printing messages.

* '''assert''': throw an error (see [https://nixos.org/manual/nix/stable/language/~~constructs~~.html?highlight=assert#assertions Nix manual: Assertions])

* '''assert''': throw an error (see [https://nixos.org/manual/nix/stable/language/syntax.html?highlight=assert#assertions Nix manual: Assertions])

The nix language also comes with some related [https://nixos.org/manual/nix/stable/language/builtins.html builtin functions]:

Line 74:

</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.

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.~~definitionsWithLocations~~</code>.

(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 19: / Line 19: @@
 The nix language has a construct to help with printing messages.
-* '''assert''': throw an error (see [https://nixos.org/manual/nix/stable/language/constructs.html?highlight=assert#assertions Nix manual: Assertions])
+* '''assert''': throw an error (see [https://nixos.org/manual/nix/stable/language/syntax.html?highlight=assert#assertions Nix manual: Assertions])
 The nix language also comes with some related [https://nixos.org/manual/nix/stable/language/builtins.html builtin functions]:
@@ Line 74: / Line 74: @@
 </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.
-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.definitionsWithLocations</code>.
+(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 ==