Merge pull request #2514 from hvitved/csharp/code-contracts

C#: Recognize Code Contract assertions

Author: calumgrant

change-notes/1.24/analysis-csharp.md

@@ -21,6 +21,7 @@ The following changes in version 1.24 affect C# analysis in all applications.
 ## Changes to libraries
 
 * The taint tracking library now tracks flow through (implicit or explicit) conversion operator calls.
+* [Code contracts](https://docs.microsoft.com/en-us/dotnet/framework/debug-trace-profile/code-contracts) are now recognized, and are treated like any other assertion methods.
 
 ## Changes to autobuilder
 

csharp/ql/src/semmle/code/csharp/commons/Assertions.qll

@@ -1,6 +1,7 @@
 /** Provides classes for assertions. */
 
 private import semmle.code.csharp.frameworks.system.Diagnostics
+private import semmle.code.csharp.frameworks.system.diagnostics.Contracts
 private import semmle.code.csharp.frameworks.test.VisualStudio
 private import semmle.code.csharp.frameworks.System
 private import ControlFlow
@@ -169,6 +170,29 @@ class SystemDiagnosticsDebugAssertTrueMethod extends AssertTrueMethod {
   }
 }
 
+/**
+ * A `System.Diagnostics.Contracts.Contract` assertion method.
+ */
+class SystemDiagnosticsContractAssertTrueMethod extends AssertTrueMethod {
+  SystemDiagnosticsContractAssertTrueMethod() {
+    exists(SystemDiagnosticsContractsContractClass c |
+      this = c.getAnAssertMethod()
+      or
+      this = c.getAnAssumeMethod()
+      or
+      this = c.getARequiresMethod()
+    )
+  }
+
+  override int getAssertionIndex() { result = 0 }
+
+  override Class getExceptionClass() {
+    // A failing assertion generates a message box, see
+    // https://docs.microsoft.com/en-us/dotnet/api/system.diagnostics.contracts.contract.assert
+    none()
+  }
+}
+
 /** A Visual Studio assertion method. */
 class VSTestAssertTrueMethod extends AssertTrueMethod {
   VSTestAssertTrueMethod() { this = any(VSTestAssertClass c).getIsTrueMethod() }

csharp/ql/src/semmle/code/csharp/frameworks/system/Diagnostics.qll

@@ -23,7 +23,7 @@ class SystemDiagnosticsDebugClass extends SystemDiagnosticsClass {
     this.isStatic()
   }
 
-  /** Gets and `Assert(bool, ...)` method. */
+  /** Gets an `Assert(bool, ...)` method. */
   Method getAssertMethod() {
     result.getDeclaringType() = this and
     result.hasName("Assert") and

csharp/ql/src/semmle/code/csharp/frameworks/system/diagnostics/Contracts.qll

@@ -0,0 +1,51 @@
+/** Provides definitions related to the namespace `System.Diagnostics.Contracts`. */
+
+import semmle.code.csharp.Type
+private import semmle.code.csharp.frameworks.system.Diagnostics
+
+/** The `System.Diagnostics.Contracts` namespace. */
+class SystemDiagnosticsContractsNamespace extends Namespace {
+  SystemDiagnosticsContractsNamespace() {
+    this.getParentNamespace() instanceof SystemDiagnosticsNamespace and
+    this.hasName("Contracts")
+  }
+}
+
+/** A class in the `System.Diagnostics.Contracts` namespace. */
+class SystemDiagnosticsContractsClass extends Class {
+  SystemDiagnosticsContractsClass() {
+    this.getNamespace() instanceof SystemDiagnosticsContractsNamespace
+  }
+}
+
+/** The `System.Diagnostics.Contracts.Contract` class. */
+class SystemDiagnosticsContractsContractClass extends SystemDiagnosticsContractsClass {
+  SystemDiagnosticsContractsContractClass() {
+    this.hasName("Contract") and
+    this.isStatic()
+  }
+
+  /** Gets an `Assert(bool, ...)` method. */
+  Method getAnAssertMethod() {
+    result.getDeclaringType() = this and
+    result.hasName("Assert") and
+    result.getParameter(0).getType() instanceof BoolType and
+    result.getReturnType() instanceof VoidType
+  }
+
+  /** Gets an `Assume(bool, ...)` method. */
+  Method getAnAssumeMethod() {
+    result.getDeclaringType() = this and
+    result.hasName("Assume") and
+    result.getParameter(0).getType() instanceof BoolType and
+    result.getReturnType() instanceof VoidType
+  }
+
+  /** Gets a `Requires(bool, ...)` method. */
+  Method getARequiresMethod() {
+    result.getDeclaringType() = this and
+    result.hasName("Requires") and
+    result.getParameter(0).getType() instanceof BoolType and
+    result.getReturnType() instanceof VoidType
+  }
+}

csharp/ql/test/library-tests/commons/Assertions/Assertions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Diagnostics.Contracts;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 public static class Forwarders
@@ -37,6 +38,18 @@ void Trivial()
         Forwarders.MyAssert2(false);
         Forwarders.MyAssert2(true);
     }
+
+    void CodeContracts(string s)
+    {
+        Contract.Requires(s != null);
+        Contract.Requires(s != null, "s must be non-null");
+        Contract.Requires<Exception>(s != null);
+        Contract.Requires<Exception>(s != null, "s must be non-null");
+        Contract.Assert(s != null);
+        Contract.Assert(s != null, "s is non-null");
+        Contract.Assume(s != null);
+        Contract.Assume(s != null, "s is non-null");
+    }
 }
 
-// semmle-extractor-options: ${testdir}/../../../resources/stubs/Microsoft.VisualStudio.TestTools.UnitTesting.cs
+// semmle-extractor-options: ${testdir}/../../../resources/stubs/Microsoft.VisualStudio.TestTools.UnitTesting.cs /r:System.Diagnostics.Contracts.dll

csharp/ql/test/library-tests/commons/Assertions/Assertions.expected

@@ -0,0 +1,33 @@
+assertTrue
+| Assertions.cs:8:44:8:59 | call to method IsTrue | Assertions.cs:8:58:8:58 | access to parameter b |
+| Assertions.cs:9:45:9:55 | call to method MyAssert | Assertions.cs:9:54:9:54 | access to parameter b |
+| Assertions.cs:17:9:17:31 | call to method Assert | Assertions.cs:17:22:17:30 | ... != ... |
+| Assertions.cs:20:9:20:32 | call to method IsTrue | Assertions.cs:20:23:20:31 | ... == ... |
+| Assertions.cs:21:9:21:32 | call to method IsTrue | Assertions.cs:21:23:21:31 | ... != ... |
+| Assertions.cs:24:9:24:38 | call to method MyAssert | Assertions.cs:24:29:24:37 | ... == ... |
+| Assertions.cs:25:9:25:39 | call to method MyAssert2 | Assertions.cs:25:30:25:38 | ... == ... |
+| Assertions.cs:30:9:30:27 | call to method Assert | Assertions.cs:30:22:30:26 | false |
+| Assertions.cs:31:9:31:26 | call to method Assert | Assertions.cs:31:22:31:25 | true |
+| Assertions.cs:32:9:32:28 | call to method IsTrue | Assertions.cs:32:23:32:27 | false |
+| Assertions.cs:33:9:33:27 | call to method IsTrue | Assertions.cs:33:23:33:26 | true |
+| Assertions.cs:36:9:36:34 | call to method MyAssert | Assertions.cs:36:29:36:33 | false |
+| Assertions.cs:37:9:37:33 | call to method MyAssert | Assertions.cs:37:29:37:32 | true |
+| Assertions.cs:38:9:38:35 | call to method MyAssert2 | Assertions.cs:38:30:38:34 | false |
+| Assertions.cs:39:9:39:34 | call to method MyAssert2 | Assertions.cs:39:30:39:33 | true |
+| Assertions.cs:44:9:44:36 | call to method Requires | Assertions.cs:44:27:44:35 | ... != ... |
+| Assertions.cs:45:9:45:58 | call to method Requires | Assertions.cs:45:27:45:35 | ... != ... |
+| Assertions.cs:46:9:46:47 | call to method Requires | Assertions.cs:46:38:46:46 | ... != ... |
+| Assertions.cs:47:9:47:69 | call to method Requires | Assertions.cs:47:38:47:46 | ... != ... |
+| Assertions.cs:48:9:48:34 | call to method Assert | Assertions.cs:48:25:48:33 | ... != ... |
+| Assertions.cs:49:9:49:51 | call to method Assert | Assertions.cs:49:25:49:33 | ... != ... |
+| Assertions.cs:50:9:50:34 | call to method Assume | Assertions.cs:50:25:50:33 | ... != ... |
+| Assertions.cs:51:9:51:51 | call to method Assume | Assertions.cs:51:25:51:33 | ... != ... |
+assertFalse
+| Assertions.cs:22:9:22:33 | call to method IsFalse | Assertions.cs:22:24:22:32 | ... != ... |
+| Assertions.cs:23:9:23:33 | call to method IsFalse | Assertions.cs:23:24:23:32 | ... == ... |
+| Assertions.cs:34:9:34:28 | call to method IsFalse | Assertions.cs:34:24:34:27 | true |
+| Assertions.cs:35:9:35:29 | call to method IsFalse | Assertions.cs:35:24:35:28 | false |
+assertNull
+| Assertions.cs:18:9:18:24 | call to method IsNull | Assertions.cs:18:23:18:23 | access to local variable s |
+assertNonNull
+| Assertions.cs:19:9:19:27 | call to method IsNotNull | Assertions.cs:19:26:19:26 | access to local variable s |

csharp/ql/test/library-tests/commons/Assertions/Assertions.ql

@@ -0,0 +1,22 @@
+import csharp
+import semmle.code.csharp.commons.Assertions
+
+query predicate assertTrue(Assertion a, Expr e) {
+  a.getExpr() = e and
+  a.getTarget() instanceof AssertTrueMethod
+}
+
+query predicate assertFalse(Assertion a, Expr e) {
+  a.getExpr() = e and
+  a.getTarget() instanceof AssertFalseMethod
+}
+
+query predicate assertNull(Assertion a, Expr e) {
+  a.getExpr() = e and
+  a.getTarget() instanceof AssertNullMethod
+}
+
+query predicate assertNonNull(Assertion a, Expr e) {
+  a.getExpr() = e and
+  a.getTarget() instanceof AssertNonNullMethod
+}

csharp/ql/test/library-tests/commons/Assertions/FailingAssertion.expected

@@ -1,5 +1,5 @@
-| Assertions.cs:29:9:29:27 | call to method Assert |
-| Assertions.cs:31:9:31:28 | call to method IsTrue |
-| Assertions.cs:33:9:33:28 | call to method IsFalse |
-| Assertions.cs:35:9:35:34 | call to method MyAssert |
-| Assertions.cs:37:9:37:35 | call to method MyAssert2 |
+| Assertions.cs:30:9:30:27 | call to method Assert |
+| Assertions.cs:32:9:32:28 | call to method IsTrue |
+| Assertions.cs:34:9:34:28 | call to method IsFalse |
+| Assertions.cs:36:9:36:34 | call to method MyAssert |
+| Assertions.cs:38:9:38:35 | call to method MyAssert2 |