Keep symbolic link after editing credentials.yml.enc

When editing credentials.yml.enc after creating a symbolic link,
the symbolic link is removed and overwritten with a normal file.
This commit changes the behavior to keep the symbolic link.

In case of using a dead symbolic link that link is revived after writing.

Fixes #36411

activesupport/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Support symbolic links for `content_path` in `ActiveSupport::EncryptedFile`.
+
+    *Takumi Shotoku*
+
 *   Improve `Range#===`, `Range#include?`, and `Range#cover?` to work with beginless (startless)
     and endless range targets.
 

activesupport/lib/active_support/encrypted_file.rb

@@ -30,7 +30,8 @@ module ActiveSupport
     attr_reader :content_path, :key_path, :env_key, :raise_if_missing_key
 
     def initialize(content_path:, key_path:, env_key:, raise_if_missing_key:)
-      @content_path, @key_path = Pathname.new(content_path), Pathname.new(key_path)
+      @content_path = Pathname.new(content_path).yield_self { |path| path.symlink? ? path.realpath : path }
+      @key_path = Pathname.new(key_path)
       @env_key, @raise_if_missing_key = env_key, raise_if_missing_key
     end
 

activesupport/test/encrypted_file_test.rb

@@ -12,9 +12,7 @@ class EncryptedFileTest < ActiveSupport::TestCase
     @key_path = File.join(Dir.tmpdir, "content.txt.key")
     File.write(@key_path, ActiveSupport::EncryptedFile.generate_key)
 
-    @encrypted_file = ActiveSupport::EncryptedFile.new(
-      content_path: @content_path, key_path: @key_path, env_key: "CONTENT_KEY", raise_if_missing_key: true
-    )
+    @encrypted_file = encrypted_file(@content_path)
   end
 
   teardown do
@@ -50,10 +48,40 @@ class EncryptedFileTest < ActiveSupport::TestCase
   end
 
   test "raise MissingKeyError when key is missing" do
-    assert_raise(ActiveSupport::EncryptedFile::MissingKeyError) do
-      ActiveSupport::EncryptedFile.new(
-        content_path: @content_path, key_path: "", env_key: "", raise_if_missing_key: true
-      ).read
+    assert_raise ActiveSupport::EncryptedFile::MissingKeyError do
+      encrypted_file(@content_path, key_path: "", env_key: "").read
     end
   end
+
+  test "respects existing content_path symlink" do
+    @encrypted_file.write(@content)
+
+    symlink_path = File.join(Dir.tmpdir, "content_symlink.txt.enc")
+    File.symlink(@encrypted_file.content_path, symlink_path)
+
+    encrypted_file(symlink_path).write(@content)
+
+    assert File.symlink?(symlink_path)
+    assert_equal @content, @encrypted_file.read
+  ensure
+    FileUtils.rm_rf symlink_path
+  end
+
+  test "creates new content_path symlink if it's dead" do
+    symlink_path = File.join(Dir.tmpdir, "content_symlink.txt.enc")
+    File.symlink(@content_path, symlink_path)
+
+    encrypted_file(symlink_path).write(@content)
+
+    assert File.exist?(@content_path)
+    assert_equal @content, @encrypted_file.read
+  ensure
+    FileUtils.rm_rf symlink_path
+  end
+
+  private
+    def encrypted_file(content_path, key_path: @key_path, env_key: "CONTENT_KEY")
+      ActiveSupport::EncryptedFile.new(content_path: @content_path, key_path: key_path,
+        env_key: env_key, raise_if_missing_key: true)
+    end
 end