Add new ProvideDefaultParameterValue rule.

Per @rkeithhill suggestion in #133

Author: GoodOlClint

Rules/ProvideDefaultParameterValue.cs

@@ -0,0 +1,117 @@
+//
+// Copyright (c) Microsoft Corporation.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+
+using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Management.Automation.Language;
+using Microsoft.Windows.Powershell.ScriptAnalyzer.Generic;
+using System.ComponentModel.Composition;
+using System.Globalization;
+
+namespace Microsoft.Windows.Powershell.ScriptAnalyzer.BuiltinRules
+{
+    /// <summary>
+    /// ProvideDefaultParameterValue: Check if any uninitialized variable is used.
+    /// </summary>
+    [Export(typeof(IScriptRule))]
+    public class ProvideDefaultParameterValue : IScriptRule
+    {
+        /// <summary>
+        /// AnalyzeScript: Check if any uninitialized variable is used.
+        /// </summary>
+        public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
+        {
+           if (ast == null) throw new ArgumentNullException(Strings.NullAstErrorMessage);
+
+            // Finds all functionAst
+            IEnumerable<Ast> functionAsts = ast.FindAll(testAst => testAst is FunctionDefinitionAst, true);
+
+            foreach (FunctionDefinitionAst funcAst in functionAsts)
+            {
+                // Finds all ParamAsts.
+                IEnumerable<Ast> varAsts = funcAst.FindAll(testAst => testAst is VariableExpressionAst, true);
+                
+                // Iterrates all ParamAsts and check if their names are on the list.
+
+                HashSet<string> paramVariables = new HashSet<string>();
+                // only raise the rules for variables in the param block.
+                if (funcAst.Body != null && funcAst.Body.ParamBlock != null && funcAst.Body.ParamBlock.Parameters != null)
+                {
+                    paramVariables.UnionWith(funcAst.Body.ParamBlock.Parameters.Select(paramAst => paramAst.Name.VariablePath.UserPath));
+                }
+
+                // Iterates all VariableExpressionAst and check the command name.
+                foreach (VariableExpressionAst varAst in varAsts)
+                {
+                    if (Helper.Instance.IsUninitialized(varAst, funcAst) && paramVariables.Contains(varAst.VariablePath.UserPath))
+                    {
+                        yield return new DiagnosticRecord(string.Format(CultureInfo.CurrentCulture, Strings.ProvideDefaultParameterValueError, varAst.VariablePath.UserPath),
+                            varAst.Extent, GetName(), DiagnosticSeverity.Warning, fileName, varAst.VariablePath.UserPath);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// GetName: Retrieves the name of this rule.
+        /// </summary>
+        /// <returns>The name of this rule</returns>
+        public string GetName()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.NameSpaceFormat, GetSourceName(), Strings.ProvideDefaultParameterValueName);
+        }
+
+        /// <summary>
+        /// GetCommonName: Retrieves the common name of this rule.
+        /// </summary>
+        /// <returns>The common name of this rule</returns>
+        public string GetCommonName()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.ProvideDefaultParameterValueCommonName);
+        }
+
+        /// <summary>
+        /// GetDescription: Retrieves the description of this rule.
+        /// </summary>
+        /// <returns>The description of this rule</returns>
+        public string GetDescription()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.ProvideDefaultParameterValueDescription);
+        }
+
+        /// <summary>
+        /// Method: Retrieves the type of the rule: builtin, managed or module.
+        /// </summary>
+        public SourceType GetSourceType()
+        {
+            return SourceType.Builtin;
+        }
+
+        /// <summary>
+        /// GetSeverity: Retrieves the severity of the rule: error, warning of information.
+        /// </summary>
+        /// <returns></returns>
+        public RuleSeverity GetSeverity()
+        {
+            return RuleSeverity.Warning;
+        }
+
+        /// <summary>
+        /// Method: Retrieves the module/assembly name the rule is from.
+        /// </summary>
+        public string GetSourceName()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.SourceName);
+        }
+    }
+}

Rules/ScriptAnalyzerBuiltinRules.csproj

@@ -59,6 +59,7 @@
     <Compile Include="AvoidReservedParams.cs" />
     <Compile Include="AvoidShouldContinueWithoutForce.cs" />
     <Compile Include="AvoidTrapStatement.cs" />
+    <Compile Include="ProvideDefaultParameterValue.cs" />
     <Compile Include="AvoidUninitializedVariable.cs" />
     <Compile Include="AvoidUsernameAndPasswordParams.cs" />
     <Compile Include="AvoidUsingComputerNameHardcoded.cs" />

Rules/Strings.Designer.cs

@@ -714,4 +714,16 @@
   <data name="DscExamplesPresentNoExamplesError" xml:space="preserve">
     <value>No examples found for resource '{0}'</value>
   </data>
+  <data name="ProvideDefaultParameterValueCommonName" xml:space="preserve">
+    <value>Default Parameter Values</value>
+  </data>
+  <data name="ProvideDefaultParameterValueDescription" xml:space="preserve">
+    <value>Parameters must have a default value. To fix a violation of this rule, please initialize non-global variables.</value>
+  </data>
+  <data name="ProvideDefaultParameterValueError" xml:space="preserve">
+    <value>Parameter '{0}' is not initialized. Non-global variables must be initialized. To fix a violation of this rule, please initialize non-global variables.</value>
+  </data>
+  <data name="ProvideDefaultParameterValueName" xml:space="preserve">
+    <value>ProvideDefaultParameterValue</value>
+  </data>
 </root>