Allow / in relative paths for using module (#7424) (#12492)

src/System.Management.Automation/engine/parser/SymbolResolver.cs

@@ -498,8 +498,8 @@ namespace System.Management.Automation.Language
                     return null;
                 }
 
-                // case 1: relative path. Relative for file in the same folder should include .\
-                bool isPath = fullyQualifiedNameStr.Contains(@"\");
+                // case 1: relative path. Relative for file in the same folder should include .\ or ./
+                bool isPath = fullyQualifiedNameStr.Contains('\\') || fullyQualifiedNameStr.Contains('/');
                 if (isPath && !LocationGlobber.IsAbsolutePath(fullyQualifiedNameStr))
                 {
                     string rootPath = Path.GetDirectoryName(_parser._fileName);

test/powershell/Language/Classes/scripting.Classes.using.tests.ps1

@@ -339,7 +339,7 @@ using module Foo
         }
     }
 
-        Context 'Side by side' {
+    Context 'Side by side' {
         BeforeAll {
             # Add side-by-side module
             $newVersion = '3.4.5'
@@ -523,6 +523,19 @@ using module FooForPaths
                 Pop-Location
             }
         }
+
+        It 'can be accessed by relative path with .<Separator>' -TestCases @(
+            @{ Separator = '\' },
+            @{ Separator = '/' }
+        ) {
+            param([string]$Separator)
+            $name = 'relative-slash-paths'
+            'function Get-TestString { "Worked" }' | Set-Content "TestDrive:\modules\$name.psm1"
+
+            "using module .$Separator$name.psm1; Get-TestString" | Set-Content "TestDrive:\modules\$name.ps1"
+
+            & "TestDrive:\modules\$name.ps1" | Should -BeExactly "Worked"
+        }
     }
 
     Context "module has non-terminating error handled with 'SilentlyContinue'" {
@@ -547,4 +560,3 @@ using module $testFile
         }
     }
 }
-