RegexLiteral: Not expanding literals within AttributeAST (Fixes #290)

Author: James Brundage

Transpilers/Syntax/RegexLiteral.psx.ps1

@@ -85,11 +85,20 @@ $($Keywords -join '|') # followed by keywords
 (?<HereDoc>@){0,1}            # Optional heredoc end
 $                        # string end.     
 '@, Options='IgnoreCase,IgnorePatternWhitespace, RightToLeft')]
+[ValidateScript({
+    $validating = $_
+    if ($validating.Parent -is [Management.Automation.Language.AttributeAST]) {
+        return $false
+    }
+    return $true
+})]
 param(
+# A RegexLiteral can be any string constant expression (as long as it's not in an attribute).
 [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='StringConstantExpressionAST')]
 [Management.Automation.Language.StringConstantExpressionAST]
 $StringConstantExpression,
 
+# It can also by any expandable string, which allows you to construct Regexes using PowerShell variables and subexpressions.
 [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='ExpandableStringExpressionAst')]
 [Management.Automation.Language.ExpandableStringExpressionAst]
 $ExpandableStringExpression

Transpilers/Syntax/RegexLiteral.tests.ps1

@@ -0,0 +1,16 @@
+describe RegexLiteral {
+    it 'Enables you write RegexLiterals in PipeScript' {
+        {'/a|b/'} | .>Pipescript | Should -Be "[regex]::new('a|b', 'IgnoreCase')"
+    }
+    it 'Can turn expandable strings into RegExes' {
+        {"/[$a$b]/"} | .>PipeScript | Should -Be '[regex]::new("[$a$b]", ''IgnoreCase'')'
+    }
+    context 'Potential pitfalls' {
+        it 'Will not escape a single slash' {
+            {'/'} | .>Pipescript | Should -Be "'/'"
+        }
+        it 'Will not process a RegexLiteral inside of an attribute' {
+            {[Reflection.AssemblyMetadata('Key','/value/')]$v}.Transpile()
+        }        
+    }
+}