typos: fix unexpected behaviour

Enable typos.configPath to be of type path. This way, we can
use excludes from .typos.toml when running
`pre-commit run typos --all-files`. Otherwise, the execution
differs from a normal invocation of typos, which is unexpected
and leads to wrong results.

To not break anything, and to be compliant with the existing
API, I modified configPath to be either a Nix path or a string.

The main motivation for this change is a repository on my machine
where pre-commit ignores directory foobar (which is excluded
by .typos.toml) but passes all 65,000 files of foobar as argument
to typos. In these situation, typos goes nuts and often the
system freezes.

So with this change, I prevent that possibly tens of thousands
of files that should not be checked in any case are passed to
typos, which results in a smooth experience.

[0]: cachix#387 (comment)

Author: phip1611

modules/hooks.nix

@@ -1436,7 +1436,7 @@ in
             configuration =
               mkOption {
                 type = types.str;
-                description = lib.mdDoc "Multiline-string configuration passed as config file. If set, config set in `typos.settings.configPath` gets ignored.";
+                description = lib.mdDoc "Multiline-string configuration passed as config file. It is recommended to use `configPath` instead for a more natural experience of typos.";
                 default = "";
                 example = ''
                   [files]
@@ -1450,11 +1450,14 @@ in
                 '';
               };
 
+            # It is recommended to use a Nix path here as this way, the excludes
+            # from the config file can be taken into account by pre-commit when
+            # running `$ pre-commit run --all-files`.
             configPath =
               mkOption {
-                type = types.str;
-                description = lib.mdDoc "Path to a custom config file.";
-                default = "";
+                type = types.nullOr (types.either types.str types.path);
+                description = lib.mdDoc "[Path](https://nixos.org/manual/nix/stable/language/values#type-path) to a typos config file (recommended) or a string (deprecated)";
+                default = null;
                 example = ".typos.toml";
               };
 
@@ -3314,6 +3317,47 @@ lib.escapeShellArgs (lib.concatMap (ext: [ "--ghc-opt" "-X${ext}" ]) hooks.ormol
           entry = "${hooks.treefmt.package}/bin/treefmt --fail-on-change";
         };
       typos =
+        let
+          # Path to config file. May be in Nix store but can also be a relative
+          # path to a system-dependent file.
+          #
+          # After various upstream discussions [0]), the best solution is to
+          # provide the config file as Nix path but keep the string passing
+          # as fall-back.
+          #
+          # [0]: https://github.com/cachix/pre-commit-hooks.nix/pull/387#issuecomment-1893600631
+          pathToConfigFile =
+            if hooks.typos.settings.configPath != null
+            # Important: If passed as typeOf == "path", this is in Nix store
+            # which we in fact encourage.
+            then hooks.typos.settings.configPath
+            else
+              builtins.toFile "config.toml"
+                # Concatenate config in config file with section for ignoring words
+                # generated from list of words to ignore
+                (hooks.typos.settings.configuration +
+                  lib.strings.optionalString (hooks.typos.settings.ignored-words != [ ]) "\n\[default.extend-words\]" +
+                  lib.strings.concatMapStrings (x: "\n${x} = \"${x}\"") hooks.typos.settings.ignored-words
+                )
+          ;
+          # If the config file path is passed as string and not as path, we
+          # can't read it from Nix.
+          excludesFromConfig =
+            if builtins.typeOf hooks.typos.settings.configPath == "path" # passed directly or as Path
+            then
+              (
+                let
+                  toml = builtins.fromTOML (builtins.readFile pathToConfigFile);
+                in
+                  /*
+                  The "files.extend-exclude" key comes from
+                  https://github.com/crate-ci/typos/blob/master/docs/reference.md
+                  */
+                  (toml.files or { }).extend-exclude or [ ]
+              )
+            else
+              [ ];
+        in
         {
           name = "typos";
           description = "Source code spell checker";
@@ -3328,8 +3372,8 @@ lib.escapeShellArgs (lib.concatMap (ext: [ "--ghc-opt" "-X${ext}" ]) hooks.ormol
                   (with hooks.typos.settings; [
                     [ binary "--binary" ]
                     [ (color != "auto") "--color ${color}" ]
-                    [ (configuration != "") "--config ${configFile}" ]
-                    [ (configPath != "" && configuration == "") "--config ${configPath}" ]
+                    # Config file always exists (we generate one if not).
+                    [ true "--config ${pathToConfigFile}" ]
                     [ diff "--diff" ]
                     [ (exclude != "") "--exclude ${exclude} --force-exclude" ]
                     [ (format != "long") "--format ${format}" ]
@@ -3345,6 +3389,7 @@ lib.escapeShellArgs (lib.concatMap (ext: [ "--ghc-opt" "-X${ext}" ]) hooks.ormol
             in
             "${hooks.typos.package}/bin/typos ${cmdArgs}";
           types = [ "text" ];
+          excludes = excludesFromConfig;
         };
       typstfmt = {
         name = "typstfmt";