Fixed empty markdown out of bounds #516 (#532)

CHANGELOG.md

@@ -6,6 +6,9 @@
 
 ## Unreleased
 
+- Bug fixes:
+  - Fixed out of bounds exception when empty markdown documentation is used. [#516](https://github.com/microsoft/PSRule/issues/516)
+
 ## v0.20.0-B2008010 (pre-release)
 
 What's changed since pre-release v0.20.0-B2008002:

src/PSRule/Commands/NewRuleDefinitionCommand.cs

@@ -9,6 +9,7 @@ using System;
 using System.Collections;
 using System.IO;
 using System.Management.Automation;
+using System.Threading;
 
 namespace PSRule.Commands
 {
@@ -72,7 +73,7 @@ namespace PSRule.Commands
         protected override void ProcessRecord()
         {
             if (!IsScriptScope())
-                throw new RuleRuntimeException(string.Format(PSRuleResources.KeywordScriptScope, LanguageKeywords.Rule));
+                throw new RuleRuntimeException(string.Format(Thread.CurrentThread.CurrentCulture, PSRuleResources.KeywordScriptScope, LanguageKeywords.Rule));
 
             var context = RunspaceContext.CurrentThread;
             var metadata = GetMetadata(MyInvocation.ScriptName, MyInvocation.ScriptLineNumber, MyInvocation.OffsetInLine);
@@ -96,6 +97,7 @@ namespace PSRule.Commands
             if (helpInfo.Synopsis == null)
                 helpInfo.Synopsis = metadata.Synopsis;
 
+#pragma warning disable CA2000 // Dispose objects before losing scope, needs to be passed to pipeline
             var block = new RuleBlock(
                 source: source,
                 ruleName: Name,
@@ -106,6 +108,7 @@ namespace PSRule.Commands
                 configuration: Configure,
                 extent: extent
             );
+#pragma warning restore CA2000 // Dispose objects before losing scope, needs to be passed to pipeline
             WriteObject(block);
         }
 
@@ -155,8 +158,13 @@ namespace PSRule.Commands
 
         private static bool TryDocument(string path, out RuleDocument document)
         {
+            document = null;
+            var markdown = File.ReadAllText(path);
+            if (string.IsNullOrEmpty(markdown))
+                return false;
+
             var reader = new MarkdownReader(yamlHeaderOnly: false);
-            var stream = reader.Read(File.ReadAllText(path), path);
+            var stream = reader.Read(markdown, path);
             var lexer = new RuleLexer();
             document = lexer.Process(stream);
             return document != null;

src/PSRule/Parser/MarkdownReader.cs

@@ -59,6 +59,9 @@ namespace PSRule.Parser
 
         public TokenStream Read(string markdown, string path)
         {
+            if (string.IsNullOrEmpty(markdown))
+                return _Output;
+
             _Context = MarkdownReaderMode.None;
             _Stream = new MarkdownStream(markdown);
 
@@ -246,7 +249,7 @@ namespace PSRule.Parser
                 _Context = MarkdownReaderMode.None;
         }
 
-        private string UnwrapStyleMarkers(MarkdownStream stream, out MarkdownTokens flag)
+        private static string UnwrapStyleMarkers(MarkdownStream stream, out MarkdownTokens flag)
         {
             flag = MarkdownTokens.None;
 
@@ -308,12 +311,12 @@ namespace PSRule.Parser
             return text;
         }
 
-        private string Pad(string text, char c, int left = 0, int right = 0)
+        private static string Pad(string text, char c, int left = 0, int right = 0)
         {
             return text.PadLeft(text.Length + left, c).PadRight(text.Length + left + right, c);
         }
 
-        private bool IsList(string text)
+        private static bool IsList(string text)
         {
             var clean = text.Trim();
 
@@ -328,7 +331,7 @@ namespace PSRule.Parser
             return false;
         }
 
-        private MarkdownTokens GetEnding(int lineEndings)
+        private static MarkdownTokens GetEnding(int lineEndings)
         {
             if (lineEndings == 0)
                 return MarkdownTokens.None;

tests/PSRule.Tests/PSRule.Common.Tests.ps1

@@ -1325,6 +1325,12 @@ Describe 'Get-PSRule' -Tag 'Get-PSRule','Common' {
                 $result | Should -Not -BeNullOrEmpty;
                 $result.RuleName | Should -Be 'WithNoSynopsis';
                 $result.Synopsis | Should -BeNullOrEmpty;
+
+                # Empty markdown
+                $result = Get-PSRule -Path $ruleFilePath -Name 'WithNoSynopsis' -Culture 'en-YY';
+                $result | Should -Not -BeNullOrEmpty;
+                $result.RuleName | Should -Be 'WithNoSynopsis';
+                $result.Synopsis | Should -BeNullOrEmpty;
             }
             finally {
                 [PSRule.Configuration.PSRuleOption]::UseCurrentCulture();