feat: initFilter allows looking other file types, ignore other than /_. (#19)

* feat: initFilter allows looking other file types, ignore other than /_.

* Update README.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: vic

README.md

@@ -2,7 +2,11 @@
 
 > Helper functions for import of [Nixpkgs module system](https://nix.dev/tutorials/module-system/) modules under a directory recursively
 
-Module class agnostic; can be used for NixOS, nix-darwin, home-manager, flake-parts, NixVim.
+- Flake callable; Easy to use, intuitive for the most common use case: `inputs.import-tree ./modules`
+- Module class agnostic; can be used for NixOS, nix-darwin, home-manager, flake-parts, NixVim.
+- Can be used outside flakes as a dependencies-free lib; Just import our `./default.nix`.
+- Can be used to list other file types, not just `.nix`. See `.initFilter`, `.files` API.
+- Extensible API. import-tree objects are customizable. See `.addAPI`.
 
 ## Quick Usage (with flake-parts)
 
@@ -29,7 +33,9 @@ you can use the import-tree API (read below for more).
 
 ## Ignored files
 
-Paths that have a component that begins with an underscore are ignored.
+By default, paths having a component that begins with an underscore (`/_`) are ignored.
+
+This can be changed by using `.initFilter` API.
 
 <details>
   <summary>
@@ -177,6 +183,8 @@ Or, in a simpler but less readable way:
 (import-tree.filter (lib.hasInfix ".mod.")).filter (lib.hasSuffix "default.nix") ./some-dir
 ```
 
+See also `import-tree.initFilter`.
+
 ### `import-tree.match` and `import-tree.matchNot`
 
 `match` takes a regular expression. The regex should match the full path for the path to be selected. Matching is done with `builtins.match`.
@@ -297,6 +305,37 @@ import-tree.leafs
 Returns a fresh import-tree with empty state. If you previously had any path, lib, filter, etc,
 you might need to set them on the new empty tree.
 
+### `import-tree.initFilter`
+
+*Replaces* the initial filter which defaults to: Include files with `.nix` suffix and not having `/_` infix.
+
+_NOTE_: initFilter is non-accumulating and is the *first* filter to run before those accumulated via `filter`/`match`.
+
+You can use this to make import-tree scan for other file types or change the ignore convention.
+
+```nix
+# import-tree.initFilter : (path -> bool) -> import-tree
+
+import-tree.initFilter (p: lib.hasSuffix ".nix" p && !lib.hasInfix "/ignored/") # nix files not inside /ignored/
+import-tree.initFilter (lib.hasSuffix ".md")  # scan for .md files everywhere, nothing ignored.
+```
+
+### `import-tree.files`
+
+A shorthand for `import-tree.leafs.result`. Returns a list of matching files.
+
+This can be used when you don't want to import the tree, but just get a list of files from it.
+
+Useful for listing files other than `.nix`, for example, for passing all `.js` files to a minifier:
+
+_TIP_: remember to use `withLib` when *not* using import-tree as a module import.
+
+```nix
+# import-tree.files : [ <list-of-files> ]
+
+((import-tree.withLib lib).initFilter (lib.hasSuffix ".js")).files # => list of all .js files
+```
+
 ### `import-tree.result`
 
 Exactly the same as calling the import-tree object with an empty list `[ ]`.

checkmate.nix

@@ -92,12 +92,12 @@ in
         };
 
         addPath."test `addPath` prepends a path to filter" = {
-          expr = (lit.addPath ./tree/x).leafs.result;
+          expr = (lit.addPath ./tree/x).files;
           expected = [ ./tree/x/y.nix ];
         };
 
         addPath."test `addPath` can be called multiple times" = {
-          expr = ((lit.addPath ./tree/x).addPath ./tree/a/b).leafs.result;
+          expr = ((lit.addPath ./tree/x).addPath ./tree/a/b).files;
           expected = [
             ./tree/x/y.nix
             ./tree/a/b/b_a.nix
@@ -106,31 +106,56 @@ in
         };
 
         addPath."test `addPath` identity" = {
-          expr = ((lit.addPath ./tree/x).addPath ./tree/a/b).leafs.result;
+          expr = ((lit.addPath ./tree/x).addPath ./tree/a/b).files;
           expected = lit.leafs [
             ./tree/x
             ./tree/a/b
           ];
         };
 
-        reset."test `new` returns a clear state" = {
+        new."test `new` returns a clear state" = {
           expr = lib.pipe lit [
             (i: i.addPath ./tree/x)
             (i: i.addPath ./tree/a/b)
             (i: i.new)
             (i: i.addPath ./tree/modules/hello-world)
             (i: i.withLib lib)
-            (i: i.leafs.result)
+            (i: i.files)
           ];
           expected = [ ./tree/modules/hello-world/mod.nix ];
         };
 
+        initFilter."test can change the initial filter to look for other file types" = {
+          expr = (lit.initFilter (p: lib.hasSuffix ".txt" p)).leafs [ ./tree/a ];
+          expected = [ ./tree/a/a.txt ];
+        };
+
+        initFilter."test initf does filter non-paths" = {
+          expr =
+            let
+              mod = (it.initFilter (x: !(x ? config.boom))) [
+                {
+                  options.hello = lib.mkOption {
+                    default = "world";
+                    type = lib.types.str;
+                  };
+                }
+                {
+                  config.boom = "boom";
+                }
+              ];
+              res = lib.modules.evalModules { modules = [ mod ]; };
+            in
+            res.config.hello;
+          expected = "world";
+        };
+
         addAPI."test extends the API available on an import-tree object" = {
           expr =
             let
               extended = lit.addAPI { helloOption = self: self.addPath ./tree/modules/hello-option; };
             in
-            extended.helloOption.leafs.result;
+            extended.helloOption.files;
           expected = [ ./tree/modules/hello-option/mod.nix ];
         };
 
@@ -139,7 +164,7 @@ in
             let
               first = lit.addAPI { helloOption = self: self.addPath ./tree/modules/hello-option; };
               second = first.addAPI { helloWorld = self: self.addPath ./tree/modules/hello-world; };
-              extended = second.addAPI { res = self: self.helloOption.leafs.result; };
+              extended = second.addAPI { res = self: self.helloOption.files; };
             in
             extended.res;
           expected = [ ./tree/modules/hello-option/mod.nix ];

default.nix

@@ -3,6 +3,7 @@ let
     {
       lib ? null,
       pipef ? null,
+      initf ? null,
       filterf,
       mapf,
       paths,
@@ -28,7 +29,7 @@ let
       leafs =
         lib: root:
         let
-          initialFilter = andNot (lib.hasInfix "/_") (lib.hasSuffix ".nix");
+          treeFiles = t: (t.withLib lib).files;
           listFilesRecursive =
             x:
             if isImportTree x then
@@ -39,9 +40,11 @@ let
               lib.filesystem.listFilesRecursive x
             else
               [ x ];
-          treeFiles = t: (t.withLib lib).leafs.result;
+          nixFilter = andNot (lib.hasInfix "/_") (lib.hasSuffix ".nix");
+          initialFilter = if initf != null then initf else nixFilter;
           pathFilter = compose (and filterf initialFilter) toString;
-          filter = x: if isPathLike x then pathFilter x else filterf x;
+          otherFilter = and filterf (if initf != null then initf else (_: true));
+          filter = x: if isPathLike x then pathFilter x else otherFilter x;
         in
         lib.pipe
           [ paths root ]
@@ -118,12 +121,16 @@ let
 
             # Configuration updates (non-accumulating)
             withLib = lib: mergeAttrs { inherit lib; };
+            initFilter = initf: mergeAttrs { inherit initf; };
             pipeTo = pipef: mergeAttrs { inherit pipef; };
             leafs = mergeAttrs { pipef = (i: i); };
 
             # Applies empty (for already path-configured trees)
             result = (self f) [ ];
 
+            # Return a list of all filtered files.
+            files = (self f).leafs.result;
+
             # returns the original empty state
             new = callable;
           };