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bergmeisterJamesWTruher
bergmeister
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JamesWTruher
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Warn when an if statement contains an assignment (#859)
* first try at implementation rule. basically works but also catches case where the execution block of the if statement contains an assignment * remove unused variables and fix test to import pssa and fix some rule counter tests * Improve rule to only assert against clause in if statement. TODO: Make sure that the following case does not get flagged up (added a test case for it) 'if ( $files = get-childitem ) { }' * Improve rule to reduce false warnings and adds lots more tests. The only false positive that is left is 'if ($a = (Get-ChildItem)){}' where the RHS is wrapped in an exprssion * fix false positive when the command is wrapped in an expression * simplify and cleanup * Uncomment import of PSSA in test to be consistent with other tests
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‎Engine/Generic/IScriptRule.cs‎

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// THE SOFTWARE.
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//
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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using System.Management.Automation.Language;
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namespace Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic

‎RuleDocumentation/PossibleIncorrectUsageOfAssignmentOperator.md‎

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# PossibleIncorrectUsageOfAssignmentOperator
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**Severity Level: Information**
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## Description
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In many programming languages, the equality operator is denoted as `==` or `=`, but `PowerShell` uses `-eq`. Since assignment inside if statements are very rare, this rule wants to call out this case because it might have been unintentional.

‎Rules/PossibleIncorrectUsageOfAssignmentOperator.cs‎

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//
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// Copyright (c) Microsoft Corporation.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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using Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic;
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using System;
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using System.Collections.Generic;
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#if !CORECLR
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using System.ComponentModel.Composition;
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#endif
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using System.Management.Automation.Language;
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using System.Globalization;
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namespace Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules
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{
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/// <summary>
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/// PossibleIncorrectUsageOfAssignmentOperator: Warn if someone uses the '=' or '==' by accident in an if statement because in most cases that is not the intention.
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/// </summary>
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#if !CORECLR
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[Export(typeof(IScriptRule))]
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#endif
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public class PossibleIncorrectUsageOfAssignmentOperator : AstVisitor, IScriptRule
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{
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/// <summary>
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/// The idea is to get all AssignmentStatementAsts and then check if the parent is an IfStatementAst, which includes if, elseif and else statements.
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/// </summary>
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public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
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{
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if (ast == null) throw new ArgumentNullException(Strings.NullAstErrorMessage);
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var ifStatementAsts = ast.FindAll(testAst => testAst is IfStatementAst, searchNestedScriptBlocks: true);
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foreach (IfStatementAst ifStatementAst in ifStatementAsts)
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{
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foreach (var clause in ifStatementAst.Clauses)
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{
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var assignmentStatementAst = clause.Item1.Find(testAst => testAst is AssignmentStatementAst, searchNestedScriptBlocks: false) as AssignmentStatementAst;
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if (assignmentStatementAst != null)
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{
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// Check if someone used '==', which can easily happen when the person is used to coding a lot in C#.
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// In most cases, this will be a runtime error because PowerShell will look for a cmdlet name starting with '=', which is technically possible to define
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if (assignmentStatementAst.Right.Extent.Text.StartsWith("="))
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{
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yield return new DiagnosticRecord(
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Strings.PossibleIncorrectUsageOfAssignmentOperatorError, assignmentStatementAst.Extent,
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GetName(), DiagnosticSeverity.Warning, fileName);
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}
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else
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{
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// If the right hand side contains a CommandAst at some point, then we do not want to warn
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// because this could be intentional in cases like 'if ($a = Get-ChildItem){ }'
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var commandAst = assignmentStatementAst.Right.Find(testAst => testAst is CommandAst, searchNestedScriptBlocks: true) as CommandAst;
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if (commandAst == null)
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{
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yield return new DiagnosticRecord(
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Strings.PossibleIncorrectUsageOfAssignmentOperatorError, assignmentStatementAst.Extent,
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GetName(), DiagnosticSeverity.Information, fileName);
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}
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}
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}
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}
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}
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}
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/// <summary>
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/// GetName: Retrieves the name of this rule.
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/// </summary>
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/// <returns>The name of this rule</returns>
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public string GetName()
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{
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return string.Format(CultureInfo.CurrentCulture, Strings.NameSpaceFormat, GetSourceName(), Strings.PossibleIncorrectUsageOfAssignmentOperatorName);
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}
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/// <summary>
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/// GetCommonName: Retrieves the common name of this rule.
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/// </summary>
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/// <returns>The common name of this rule</returns>
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public string GetCommonName()
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{
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return string.Format(CultureInfo.CurrentCulture, Strings.PossibleIncorrectUsageOfAssignmentOperatorCommonName);
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}
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/// <summary>
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/// GetDescription: Retrieves the description of this rule.
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/// </summary>
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/// <returns>The description of this rule</returns>
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public string GetDescription()
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{
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return string.Format(CultureInfo.CurrentCulture, Strings.AvoidUsingWriteHostDescription);
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}
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/// <summary>
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/// GetSourceType: Retrieves the type of the rule: builtin, managed or module.
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/// </summary>
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public SourceType GetSourceType()
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{
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return SourceType.Builtin;
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}
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/// <summary>
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/// GetSeverity: Retrieves the severity of the rule: error, warning of information.
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/// </summary>
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/// <returns></returns>
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public RuleSeverity GetSeverity()
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{
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return RuleSeverity.Information;
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}
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/// <summary>
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/// GetSourceName: Retrieves the module/assembly name the rule is from.
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/// </summary>
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public string GetSourceName()
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{
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return string.Format(CultureInfo.CurrentCulture, Strings.SourceName);
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}
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}
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}

‎Rules/Strings.Designer.cs‎

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‎Rules/Strings.resx‎

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<?xml version="1.0" encoding="utf-8"?>
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<root>
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<!--
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Microsoft ResX Schema
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<!--
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Microsoft ResX Schema
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Version 2.0
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The primary goals of this format is to allow a simple XML format
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that is mostly human readable. The generation and parsing of the
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various data types are done through the TypeConverter classes
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The primary goals of this format is to allow a simple XML format
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that is mostly human readable. The generation and parsing of the
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various data types are done through the TypeConverter classes
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associated with the data types.
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Example:
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... ado.net/XML headers & schema ...
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<resheader name="resmimetype">text/microsoft-resx</resheader>
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<resheader name="version">2.0</resheader>
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<value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
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<comment>This is a comment</comment>
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</data>
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There are any number of "resheader" rows that contain simple
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There are any number of "resheader" rows that contain simple
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name/value pairs.
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Each data row contains a name, and value. The row also contains a
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type or mimetype. Type corresponds to a .NET class that support
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text/value conversion through the TypeConverter architecture.
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Classes that don't support this are serialized and stored with the
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Each data row contains a name, and value. The row also contains a
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type or mimetype. Type corresponds to a .NET class that support
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text/value conversion through the TypeConverter architecture.
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Classes that don't support this are serialized and stored with the
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mimetype set.
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The mimetype is used for serialized objects, and tells the
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ResXResourceReader how to depersist the object. This is currently not
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The mimetype is used for serialized objects, and tells the
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ResXResourceReader how to depersist the object. This is currently not
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extensible. For a given mimetype the value must be set accordingly:
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Note - application/x-microsoft.net.object.binary.base64 is the format
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that the ResXResourceWriter will generate, however the reader can
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Note - application/x-microsoft.net.object.binary.base64 is the format
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that the ResXResourceWriter will generate, however the reader can
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read any of the formats listed below.
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mimetype: application/x-microsoft.net.object.binary.base64
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value : The object must be serialized with
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value : The object must be serialized with
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: System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
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: and then encoded with base64 encoding.
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mimetype: application/x-microsoft.net.object.soap.base64
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value : The object must be serialized with
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value : The object must be serialized with
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: System.Runtime.Serialization.Formatters.Soap.SoapFormatter
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: and then encoded with base64 encoding.
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mimetype: application/x-microsoft.net.object.bytearray.base64
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value : The object must be serialized into a byte array
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value : The object must be serialized into a byte array
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: using a System.ComponentModel.TypeConverter
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: and then encoded with base64 encoding.
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-->
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<data name="UseConsistentWhitespaceErrorSeparatorSemi" xml:space="preserve">
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<value>Use space after a semicolon.</value>
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</data>
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<data name="UseSupportsShouldProcessName" xml:space="preserve">
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<value>UseSupportsShouldProcess</value>
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</data>
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<data name="AlignAssignmentStatementError" xml:space="preserve">
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<value>Assignment statements are not aligned</value>
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</data>
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</root>
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<data name="PossibleIncorrectUsageOfAssignmentOperatorCommonName" xml:space="preserve">
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<value>'=' operator means assignment. Did you mean the equal operator '-eq'?</value>
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</data>
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<data name="PossibleIncorrectUsageOfAssignmentOperatorError" xml:space="preserve">
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<value>Did you really mean to make an assignment inside an if statement? If you rather meant to check for equality, use the '-eq' operator.</value>
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</data>
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<data name="PossibleIncorrectUsageOfAssignmentOperatorName" xml:space="preserve">
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<value>PossibleIncorrectUsageOfAssignmentOperator</value>
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</data>
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</root>

‎Tests/Engine/GetScriptAnalyzerRule.tests.ps1‎

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It "get Rules with no parameters supplied" {
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$defaultRules = Get-ScriptAnalyzerRule
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$expectedNumRules = 52
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$expectedNumRules = 53
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if ((Test-PSEditionCoreClr) -or (Test-PSVersionV3) -or (Test-PSVersionV4))
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{
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# for PSv3 PSAvoidGlobalAliases is not shipped because
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It "filters rules based on multiple severity inputs"{
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$rules = Get-ScriptAnalyzerRule -Severity Error,Information
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$rules.Count | Should be 14
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$rules.Count | Should be 15
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}
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It "takes lower case inputs" {

‎Tests/Rules/PossibleIncorrectUsageOfAssignmentOperator.tests.ps1‎

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Import-Module PSScriptAnalyzer
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$ruleName = "PSPossibleIncorrectUsageOfAssignmentOperator"
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Describe "PossibleIncorrectUsageOfAssignmentOperator" {
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Context "When there are violations" {
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It "assignment inside if statement causes warning" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a=$b){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "assignment inside if statement causes warning when when wrapped in command expression" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a=($b)){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "assignment inside if statement causes warning when wrapped in expression" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a="$b"){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "assignment inside elseif statement causes warning" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a -eq $b){}elseif($a = $b){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "double equals inside if statement causes warning" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a == $b){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "double equals inside if statement causes warning when wrapping it in command expresion" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a == ($b)){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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It "double equals inside if statement causes warning when wrapped in expression" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a == "$b"){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 1
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}
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}
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Context "When there are no violations" {
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It "returns no violations when there is no equality operator" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a -eq $b){$a=$b}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 0
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}
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It "returns no violations when there is an evaluation on the RHS" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a = Get-ChildItem){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 0
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}
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It "returns no violations when there is an evaluation on the RHS wrapped in an expression" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a = (Get-ChildItem)){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 0
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}
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It "returns no violations when there is an evaluation on the RHS wrapped in an expression and also includes a variable" {
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$warnings = Invoke-ScriptAnalyzer -ScriptDefinition 'if ($a = (Get-ChildItem $b)){}' | Where-Object {$_.RuleName -eq $ruleName}
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$warnings.Count | Should Be 0
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}
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}
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}

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