C#: Fix params attribute argument extraction

Author: tamasvajk

csharp/extractor/Semmle.Extraction.CSharp/Entities/Attribute.cs

@@ -82,10 +82,16 @@ private void ExtractArguments(TextWriter trapFile)
                 var paramName = Symbol.AttributeConstructor?.Parameters[i].Name;
                 var argSyntax = ctorArguments?.SingleOrDefault(a => a.NameColon is not null && a.NameColon.Name.Identifier.Text == paramName);
 
+                var isParamsParameter = false;
+
                 if (argSyntax is null &&                            // couldn't find named argument
                     ctorArguments?.Count > childIndex &&            // there're more arguments
                     ctorArguments[childIndex].NameColon is null)    // the argument is positional
                 {
+                    // The current argument is not named
+                    // so the previous ones were also not named
+                    // so the child index matches the parameter index.
+                    isParamsParameter = Symbol?.AttributeConstructor?.Parameters[childIndex].IsParams == true;
                     argSyntax = ctorArguments[childIndex];
                 }
 
@@ -94,6 +100,28 @@ private void ExtractArguments(TextWriter trapFile)
                     argSyntax?.Expression,
                     this,
                     childIndex++);
+
+                if (isParamsParameter &&
+                    ctorArguments is not null)
+                {
+                    // The current argument is a params argument, so we're processing all the remaining arguments:
+                    while (childIndex < ctorArguments.Count)
+                    {
+                        if (ctorArguments[childIndex].Expression is null)
+                        {
+                            // This shouldn't happen
+                            continue;
+                        }
+
+                        CreateExpressionFromArgument(
+                            constructorArgument,
+                            ctorArguments[childIndex].Expression,
+                            this,
+                            childIndex);
+
+                        childIndex++;
+                    }
+                }
             }
 
             foreach (var namedArgument in Symbol.NamedArguments)

csharp/ql/test/library-tests/attributes/AttributeArguments.expected

@@ -93,9 +93,13 @@ arguments
 | attributes.cs:141:6:141:11 | [Params(...)] | 0 | attributes.cs:141:13:141:15 | "a" |
 | attributes.cs:141:6:141:11 | [Params(...)] | 1 | attributes.cs:141:18:141:20 | "b" |
 | attributes.cs:141:6:141:11 | [Params(...)] | 2 | attributes.cs:141:23:141:23 | 1 |
+| attributes.cs:141:6:141:11 | [Params(...)] | 3 | attributes.cs:141:26:141:26 | 2 |
+| attributes.cs:141:6:141:11 | [Params(...)] | 4 | attributes.cs:141:29:141:29 | 3 |
 | attributes.cs:144:6:144:11 | [Params(...)] | 0 | attributes.cs:144:17:144:19 | "a" |
 | attributes.cs:144:6:144:11 | [Params(...)] | 1 | attributes.cs:144:26:144:28 | "b" |
 | attributes.cs:144:6:144:11 | [Params(...)] | 2 | attributes.cs:144:31:144:31 | 1 |
+| attributes.cs:144:6:144:11 | [Params(...)] | 3 | attributes.cs:144:34:144:34 | 2 |
+| attributes.cs:144:6:144:11 | [Params(...)] | 4 | attributes.cs:144:37:144:37 | 3 |
 | attributes.cs:147:6:147:11 | [Params(...)] | 0 | attributes.cs:147:35:147:37 | "a" |
 | attributes.cs:147:6:147:11 | [Params(...)] | 1 | attributes.cs:147:26:147:28 | "b" |
 | attributes.cs:147:6:147:11 | [Params(...)] | 2 | attributes.cs:147:19:147:19 | 1 |
@@ -185,9 +189,13 @@ constructorArguments
 | attributes.cs:141:6:141:11 | [Params(...)] | 0 | attributes.cs:141:13:141:15 | "a" |
 | attributes.cs:141:6:141:11 | [Params(...)] | 1 | attributes.cs:141:18:141:20 | "b" |
 | attributes.cs:141:6:141:11 | [Params(...)] | 2 | attributes.cs:141:23:141:23 | 1 |
+| attributes.cs:141:6:141:11 | [Params(...)] | 3 | attributes.cs:141:26:141:26 | 2 |
+| attributes.cs:141:6:141:11 | [Params(...)] | 4 | attributes.cs:141:29:141:29 | 3 |
 | attributes.cs:144:6:144:11 | [Params(...)] | 0 | attributes.cs:144:17:144:19 | "a" |
 | attributes.cs:144:6:144:11 | [Params(...)] | 1 | attributes.cs:144:26:144:28 | "b" |
 | attributes.cs:144:6:144:11 | [Params(...)] | 2 | attributes.cs:144:31:144:31 | 1 |
+| attributes.cs:144:6:144:11 | [Params(...)] | 3 | attributes.cs:144:34:144:34 | 2 |
+| attributes.cs:144:6:144:11 | [Params(...)] | 4 | attributes.cs:144:37:144:37 | 3 |
 | attributes.cs:147:6:147:11 | [Params(...)] | 0 | attributes.cs:147:35:147:37 | "a" |
 | attributes.cs:147:6:147:11 | [Params(...)] | 1 | attributes.cs:147:26:147:28 | "b" |
 | attributes.cs:147:6:147:11 | [Params(...)] | 2 | attributes.cs:147:19:147:19 | 1 |

csharp/ql/test/library-tests/attributes/PrintAst.expected

@@ -427,6 +427,8 @@ attributes.cs:
 #  141|         0: [StringLiteralUtf16] "a"
 #  141|         1: [StringLiteralUtf16] "b"
 #  141|         2: [IntLiteral] 1
+#  141|         3: [IntLiteral] 2
+#  141|         4: [IntLiteral] 3
 #  142|     4: [BlockStmt] {...}
 #  145|   7: [Method] M2
 #  145|     -1: [TypeMention] Void
@@ -436,6 +438,8 @@ attributes.cs:
 #  144|         0: [StringLiteralUtf16] "a"
 #  144|         1: [StringLiteralUtf16] "b"
 #  144|         2: [IntLiteral] 1
+#  144|         3: [IntLiteral] 2
+#  144|         4: [IntLiteral] 3
 #  145|     4: [BlockStmt] {...}
 #  148|   8: [Method] M3
 #  148|     -1: [TypeMention] Void