From fad6033fca96a90be36cb04f2779e0bbf7158af5 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Thu, 21 Jul 2022 13:24:03 +0200
Subject: [PATCH] Add extraRules to gitignoreFilterWith

---
 docs/gitignoreFilter.md | 10 ++++++----
 find-files.nix          | 15 +++++++++------
 tests/default.nix       | 16 ++++++++++++++++
 3 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/docs/gitignoreFilter.md b/docs/gitignoreFilter.md
index dbe1435..09089b0 100644
--- a/docs/gitignoreFilter.md
+++ b/docs/gitignoreFilter.md
@@ -14,16 +14,18 @@ for paths at or below this root path.
 ```nix
 let
   gitignore = (import (import ./nix/sources.nix)."gitignore.nix" { inherit lib; });
-  inherit (gitignore) gitignoreFilter;
+  inherit (gitignore) gitignoreFilterWith;
 
   customerFilter = src:
     let
       # IMPORTANT: use a let binding like this to memoize info about the git directories.
-      srcIgnored = gitignoreFilter src;
+      srcIgnored = gitignoreFilterWith { basePath = src; extraRules = ''
+        *.xml
+        !i-need-this.xml
+      ''; };
     in
       path: type:
-         srcIgnored path type
-           || builtins.baseNameOf path == "i-need-this.xml";
+         srcIgnored path type && baseNameOf path != "just-an-example-of-custom-filter-code.out";
 
   name = "example";
   exampleSrc = ./.;
diff --git a/find-files.nix b/find-files.nix
index 23e9177..5d7c560 100644
--- a/find-files.nix
+++ b/find-files.nix
@@ -20,9 +20,12 @@ rec {
   gitignoreFilter = basePath:
     gitignoreFilterWith { inherit basePath; };
 
-  gitignoreFilterWith = { basePath }:
+  gitignoreFilterWith = { basePath, extraRules ? null, extraRulesWithContextDir ? [] }:
+    assert extraRules == null || builtins.typeOf extraRules == "string";
     let
-      patternsBelowP = findPatternsTree basePath;
+      extraRules2 = extraRulesWithContextDir ++ 
+        lib.optional (extraRules != null) { contextDir = basePath; rules = extraRules; };
+      patternsBelowP = findPatternsTree extraRules2 basePath;
       basePathStr = toString basePath;
     in
       path: type: let
@@ -60,11 +63,11 @@ rec {
      The patterns are mixed into the attrsets using the special key "/patterns".
      Leaves are simply {}
    */
-  findPatternsTree = dir:
+  findPatternsTree = extraRules: dir:
     let
-      listOfStartingPatterns = map ({contextDir, file, ...}: 
-                                 parse-gitignore.gitignoreFilter (readFile file) contextDir
-                              ) (findAncestryGitignores dir);
+      listOfStartingPatterns = map ({contextDir, rules ? readFile file, file ? throw "gitignore.nix: A `file` or `rules` attribute is required in extraRulesWithContextDir items.", ...}: 
+                                 parse-gitignore.gitignoreFilter rules contextDir
+                              ) (findAncestryGitignores dir ++ extraRules);
       startingPatterns = builtins.foldl'
                            parse-gitignore.mergePattern
                            (defaultPatterns dir) # not the unit of merge but a set of defaults
diff --git a/tests/default.nix b/tests/default.nix
index 4eef480..a02acfa 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -22,4 +22,20 @@ in
   subdir-9 = runner.makeTest { name = "subdir-9"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "9-expected"; };
   subdir-10 = runner.makeTest { name = "subdir-10"; rootDir = testdata.sourceUnfiltered + "/test-tree"; subpath = "10-subdir-ignoring-itself"; };
 
+  unit-tests =
+    let gitignoreNix = import ../default.nix { inherit (pkgs) lib; };
+        inherit (gitignoreNix) gitignoreFilterWith;
+        example = gitignoreFilterWith { basePath = ./.; extraRules = ''
+          *.foo
+          !*.bar
+        ''; };
+    in
+
+    # Test that extraRules works:
+    assert example ./x.foo "regular" == false;
+    assert example ./x.bar "regular" == true;
+    assert example ./x.qux "regular" == true;
+
+    # End of test. (a drv to show a buildable attr when successful)
+    pkgs.emptyFile or null;
 }
\ No newline at end of file