fix unescaping single quote and add test

Author: SteveL-MSFT

dsc/examples/multiline.dsc.yaml

@@ -1,9 +1,13 @@
 $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
 resources:
-- name: test
+- name: test multi-line
   type: Test/Echo
   properties:
     output: |
       This is a
-      multi-line
+      'multi-line'
       string.
+- name: test single-quote escaping
+  type: Test/Echo
+  properties:
+    output: "[concat('This is a single-quote: ', '''')]"

dsc/tests/dsc_expressions.tests.ps1

@@ -70,9 +70,10 @@ resources:
       $LASTEXITCODE | Should -Be 0
       $out.results[0].result.actualState.output | Should -BeExactly @"
 This is a
-multi-line
+'multi-line'
 string.
 
-"@
+"@.Replace("`r", "")
+      $out.results[1].result.actualState.output | Should -BeExactly "This is a single-quote: '"
     }
 }

dsc_lib/src/parser/functions.rs

@@ -97,7 +97,8 @@ fn convert_args_node(statement_bytes: &[u8], args: &Option<Node>) -> Result<Opti
         match arg.kind() {
             "string" => {
                 let value = arg.utf8_text(statement_bytes)?;
-                result.push(FunctionArg::Value(Value::String(value.to_string())));
+                // Resolve escaped single quotes
+                result.push(FunctionArg::Value(Value::String(value.to_string().replace("''", "'"))));
             },
             "number" => {
                 let value = arg.utf8_text(statement_bytes)?;