🩹 [Patch]: Reserved words in Lua input now detected with option to skip validation (#6)

* Add reserved word checks for Lua variable names and table keys in conversion functions

* Add SkipValidation parameter to allow warnings for reserved words in Lua parsing

* Refactor ConvertFrom-Lua to use a hashtable for parameters and improve error message for reserved words in Read-LuaTable

* Fix PSScriptAnalyzer linter warnings: align assignment operators in ConvertFrom-Lua hashtable; resolve indentation inconsistency in Read-LuaTable by inlining throw message

* Fix case-sensitive reserved word checks: use -cin instead of -in per Lua §3.1; add tests for capitalized identifiers (End, While)

Author: MariusStorhaug

src/functions/private/ConvertFrom-LuaTable.ps1

@@ -22,7 +22,11 @@
 
         # Maximum allowed nesting depth.
         [Parameter()]
-        [int] $MaxDepth = 1024
+        [int] $MaxDepth = 1024,
+
+        # Skip strict Lua grammar validation. Warnings are emitted instead of terminating errors.
+        [Parameter()]
+        [switch] $SkipValidation
     )
 
     begin {}
@@ -33,6 +37,7 @@
         $script:luaAsPSCustomObject = $AsPSCustomObject.IsPresent
         $script:luaMaxDepth = $MaxDepth
         $script:luaCurrentDepth = 0
+        $script:luaSkipValidation = $SkipValidation.IsPresent
 
         Skip-LuaWhitespace
 
@@ -81,6 +86,14 @@
         }
 
         if ($assignmentDetected) {
+            # Lua 5.4 reserved words per §3.1
+            $reservedWords = @(
+                'and', 'break', 'do', 'else', 'elseif', 'end',
+                'false', 'for', 'function', 'goto', 'if', 'in',
+                'local', 'nil', 'not', 'or', 'repeat', 'return',
+                'then', 'true', 'until', 'while'
+            )
+
             # Parse one or more assignment statements into an ordered dictionary
             $assignments = [ordered]@{}
             while ($script:luaPos -lt $script:luaString.Length) {
@@ -100,6 +113,15 @@
                 }
                 $varName = $script:luaString.Substring($identStart, $script:luaPos - $identStart)
 
+                # Lua grammar: variable names cannot be reserved words (§3.1)
+                if ($varName -cin $reservedWords) {
+                    if ($script:luaSkipValidation) {
+                        Write-Warning "Reserved word '$varName' used as a variable name at position $identStart."
+                    } else {
+                        throw "Reserved word '$varName' cannot be used as a variable name at position $identStart."
+                    }
+                }
+
                 Skip-LuaWhitespace
 
                 # Expect '='

src/functions/private/ConvertTo-LuaTable.ps1

@@ -58,7 +58,7 @@
         # Enum handling
         if ($InputObject -is [enum]) {
             if ($EnumsAsStrings) {
-                $escaped = $InputObject.ToString() -replace '\\', '\\\\' -replace '"', '\"'
+                $escaped = $InputObject.ToString() -replace '\\', '\\' -replace '"', '\"'
                 return "`"$escaped`""
             }
             $underlyingType = [System.Enum]::GetUnderlyingType($InputObject.GetType())

src/functions/private/Read-LuaTable.ps1

@@ -13,6 +13,14 @@
     begin {}
 
     process {
+        # Lua 5.4 reserved words per §3.1
+        $reservedWords = @(
+            'and', 'break', 'do', 'else', 'elseif', 'end',
+            'false', 'for', 'function', 'goto', 'if', 'in',
+            'local', 'nil', 'not', 'or', 'repeat', 'return',
+            'then', 'true', 'until', 'while'
+        )
+
         $script:luaCurrentDepth++
         if ($script:luaCurrentDepth -gt $script:luaMaxDepth) {
             throw "Maximum nesting depth ($($script:luaMaxDepth)) exceeded."
@@ -78,6 +86,14 @@
 
                 if ($script:luaPos -lt $script:luaString.Length -and
                     $script:luaString[$script:luaPos] -eq '=') {
+                    # Lua grammar: Name cannot be a reserved word (§3.1)
+                    if ($ident -cin $reservedWords) {
+                        if ($script:luaSkipValidation) {
+                            Write-Warning "Reserved word '$ident' used as a bare identifier key at position $identStart."
+                        } else {
+                            throw "Reserved word '$ident' cannot be used as a bare identifier key. Use bracket notation: [`"$ident`"] = value."
+                        }
+                    }
                     # Key = value pair
                     $script:luaPos++ # skip =
                     Skip-LuaWhitespace

src/functions/public/Lua/ConvertFrom-Lua.ps1

@@ -77,13 +77,23 @@
 
         # Output arrays as a single object instead of enumerating elements through the pipeline.
         [Parameter()]
-        [switch] $NoEnumerate
+        [switch] $NoEnumerate,
+
+        # Skip strict Lua grammar validation (e.g., reserved words as bare keys). Warnings are emitted instead of errors.
+        [Parameter()]
+        [switch] $SkipValidation
     )
 
     begin {}
 
     process {
-        $result = ConvertFrom-LuaTable -InputString $InputObject -AsPSCustomObject:(-not $AsHashtable) -MaxDepth $Depth
+        $convertParams = @{
+            InputString      = $InputObject
+            AsPSCustomObject = -not $AsHashtable
+            MaxDepth         = $Depth
+            SkipValidation   = $SkipValidation.IsPresent
+        }
+        $result = ConvertFrom-LuaTable @convertParams
         if ($NoEnumerate -and $result -is [System.Array]) {
             Write-Output -InputObject $result -NoEnumerate
         } else {

tests/Lua.Tests.ps1

@@ -507,6 +507,68 @@ B = { val = 2 }
         It 'Throws on assignment with missing value' {
             { ConvertFrom-Lua -InputObject 'A = ' } | Should -Throw '*Unexpected end of input*'
         }
+
+        It 'Throws on reserved word as bare table key' {
+            { ConvertFrom-Lua -InputObject '{ end = 1 }' } | Should -Throw '*Reserved word*'
+        }
+
+        It 'Throws on reserved word as bare table key (while)' {
+            { ConvertFrom-Lua -InputObject '{ while = "loop" }' } | Should -Throw '*Reserved word*'
+        }
+
+        It 'Allows reserved words in bracket notation' {
+            $result = ConvertFrom-Lua -InputObject '{ ["end"] = 1, ["while"] = 2 }' -AsHashtable
+            $result['end'] | Should -Be 1
+            $result['while'] | Should -Be 2
+        }
+
+        It 'Allows capitalized reserved words as bare table keys (Lua keywords are case-sensitive)' {
+            $result = ConvertFrom-Lua -InputObject '{ End = 1, While = "loop" }' -AsHashtable
+            $result['End'] | Should -Be 1
+            $result['While'] | Should -Be 'loop'
+        }
+
+        It 'Allows capitalized reserved words as assignment variable names (Lua keywords are case-sensitive)' {
+            $result = ConvertFrom-Lua -InputObject 'End = 1' -AsHashtable
+            $result['End'] | Should -Be 1
+        }
+
+        It 'Throws on reserved word as assignment variable name' {
+            { ConvertFrom-Lua -InputObject 'end = 1' } | Should -Throw '*Reserved word*'
+        }
+
+        It 'Throws on reserved word as assignment variable name (while as assignment)' {
+            { ConvertFrom-Lua -InputObject 'while = 42' } | Should -Throw '*Reserved word*'
+        }
+
+        It 'SkipValidation allows reserved word as bare table key with warning' {
+            $result = ConvertFrom-Lua -InputObject '{ end = 1 }' -AsHashtable -SkipValidation 3>&1
+            $warnings = $result | Where-Object { $_ -is [System.Management.Automation.WarningRecord] }
+            $output = $result | Where-Object { $_ -isnot [System.Management.Automation.WarningRecord] }
+            $warnings.Message | Should -BeLike '*Reserved word*end*'
+            $output['end'] | Should -Be 1
+        }
+
+        It 'SkipValidation allows reserved word as assignment variable name with warning' {
+            $result = ConvertFrom-Lua -InputObject 'end = 1' -AsHashtable -SkipValidation 3>&1
+            $warnings = $result | Where-Object { $_ -is [System.Management.Automation.WarningRecord] }
+            $output = $result | Where-Object { $_ -isnot [System.Management.Automation.WarningRecord] }
+            $warnings.Message | Should -BeLike '*Reserved word*end*'
+            $output['end'] | Should -Be 1
+        }
+
+        It 'SkipValidation emits a warning for each reserved word occurrence' {
+            $result = ConvertFrom-Lua -InputObject '{ end = 1, while = 2, for = 3 }' -AsHashtable -SkipValidation 3>&1
+            $warnings = @($result | Where-Object { $_ -is [System.Management.Automation.WarningRecord] })
+            $output = $result | Where-Object { $_ -isnot [System.Management.Automation.WarningRecord] }
+            $warnings.Count | Should -Be 3
+            $warnings[0].Message | Should -BeLike '*end*'
+            $warnings[1].Message | Should -BeLike '*while*'
+            $warnings[2].Message | Should -BeLike '*for*'
+            $output['end'] | Should -Be 1
+            $output['while'] | Should -Be 2
+            $output['for'] | Should -Be 3
+        }
     }
 
     Context 'Pipeline input' {