Enable ruby to support path length >260 characters

It also needs to be enabled in the registry.
See https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=powershell#enable-long-paths-in-windows-10-version-1607-and-later
and ruby/ruby#4505

.github/workflows/ci.yml

@@ -87,6 +87,11 @@ jobs:
           echo.%GIT_REF_TAG% | findstr /C:"%target_ruby%">nul || (echo stop build not required for release & (exit 1))
         )
 
+    - name: enable long paths on OS level
+      shell: powershell
+      # https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=powershell
+      run: New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name "LongPathsEnabled" -Value 1 -PropertyType DWORD -Force
+
     - name: ensure bundler is installed on the build ruby
       run: gem install bundler --conservative --no-doc
 

appveyor.yml

@@ -10,6 +10,9 @@ init:
   - IF DEFINED DEPLOY_TAG (
       echo.%DEPLOY_TAG% | findstr /C:"%target_ruby%">nul || (echo stop build not required for release & (exit 1))
     )
+  # enable long paths on OS level:
+  # https://docs.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation?tabs=powershell
+  - powershell New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem" -Name "LongPathsEnabled" -Value 1 -PropertyType DWORD -Force
 
 install:
   # Avoid repo.msys2.org since it's down currently

recipes/sandbox/60-side-by-side-assembly.rake

@@ -35,6 +35,11 @@ end.each do |destpath|
     image = File.binread(t.prerequisites.first)
     # The XML elements we want to add to the default MINGW manifest:
     new = <<-EOT
+      <application xmlns="urn:schemas-microsoft-com:asm.v3">
+        <windowsSettings xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
+          <ws2:longPathAware>true</ws2:longPathAware>
+        </windowsSettings>
+      </application>
       <dependency>
         <dependentAssembly>
           <assemblyIdentity version="1.0.0.0" type="win32" name="ruby_builtin_dlls" />

test/test_long_path.rb

@@ -0,0 +1,30 @@
+#frozen_string_literal: true
+require "minitest/autorun"
+require "tmpdir"
+
+class TestStdlib < Minitest::Test
+  LONG_PATH = Dir.mktmpdir("0123456789"*15)
+
+  def test_mkdir
+    n = File.join(LONG_PATH, "c"*150)
+    Dir.mkdir n
+    assert Dir.exist?(n)
+    assert_operator 260, :<, n.size
+  end
+
+  def test_file_rw
+    n = File.join(LONG_PATH, "d"*150)
+    File.write n, "abc"
+    assert_equal "abc", File.read(n)
+    assert File.exist?(n)
+    assert_operator 260, :<, n.size
+  end
+
+  def test_load
+    n = File.join(LONG_PATH, "e"*150 + ".rb")
+    File.write n, "def loaded_a; 41; end"
+    assert load(n)
+    assert_equal 41, loaded_a
+    assert_operator 260, :<, n.size
+  end
+end