[Java] Add CharacterLiteral to CompileTimeConstantExpr.getStringValue

Author: JLLeitschuh

java/ql/lib/change-notes/2022-03-03-char-literal-in-compile-time-constant.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+ * Add support for `CharacterLiteral` in `CompileTimeConstantExpr.getStringValue()`

java/ql/lib/semmle/code/java/Expr.qll

@@ -168,6 +168,8 @@ class CompileTimeConstantExpr extends Expr {
   string getStringValue() {
     result = this.(StringLiteral).getValue()
     or
+    result = this.(CharacterLiteral).getValue()
+    or
     result =
       this.(AddExpr).getLeftOperand().(CompileTimeConstantExpr).getStringValue() +
         this.(AddExpr).getRightOperand().(CompileTimeConstantExpr).getStringValue()

java/ql/test/library-tests/constants/CompileTimeConstantExpr.expected

@@ -15,3 +15,4 @@
 | constants/Constants.java:20:22:20:22 | 5 |
 | constants/Constants.java:20:27:20:27 | 1 |
 | constants/Constants.java:20:31:20:31 | 2 |
+| constants/Constants.java:21:22:21:24 | 'a' |

java/ql/test/library-tests/constants/PrintAst.expected

@@ -66,7 +66,11 @@ constants/Constants.java:
 #   20|                 1: [IntegerLiteral] 5
 #   20|               1: [IntegerLiteral] 1
 #   20|               2: [IntegerLiteral] 2
-#   22|         11: [ReturnStmt] return ...
+#   21|         11: [LocalVariableDeclStmt] var ...;
+#   21|           0: [TypeAccess] char
+#   21|           1: [LocalVariableDeclExpr] charLiteral
+#   21|             0: [CharacterLiteral] 'a'
+#   23|         12: [ReturnStmt] return ...
 constants/Initializers.java:
 #    0| [CompilationUnit] Initializers
 #    3|   1: [Class] Initializers
@@ -512,3 +516,13 @@ constants/Values.java:
 #   90|           0: [TypeAccess] int
 #   90|           1: [LocalVariableDeclExpr] var_nonfinald_local
 #   90|             0: [VarAccess] var_field
+#   91|         68: [LocalVariableDeclStmt] var ...;
+#   91|           0: [TypeAccess] String
+#   91|           1: [LocalVariableDeclExpr] concatinatedString
+#   91|             0: [StringLiteral] "a" + "b"
+#   92|         69: [LocalVariableDeclStmt] var ...;
+#   92|           0: [TypeAccess] String
+#   92|           1: [LocalVariableDeclExpr] concatinatedChar
+#   92|             0: [AddExpr] ... + ...
+#   92|               0: [StringLiteral] "ab"
+#   92|               1: [CharacterLiteral] 'c'

java/ql/test/library-tests/constants/constants/Constants.java

@@ -18,6 +18,7 @@ void constants(final int notConstant) {
 		int paren = (12);
 		String string = "a string";
 		int ternary = (3 < 5) ? 1 : 2;
+		char charLiteral = 'a';
 
 		return;
 	}

java/ql/test/library-tests/constants/constants/Values.java

@@ -88,5 +88,7 @@ void values(final int notConstant) {
         int var_local = final_local; //42
         int var_param = notConstant; //Not constant
         int var_nonfinald_local = var_field; //Not constant
+        String concatinatedString = "a" + "b"; //ab
+        String concatinatedChar = "ab" + 'c'; //abc
     }
 }

java/ql/test/library-tests/constants/getStringValue.expected

@@ -0,0 +1,3 @@
+| constants/Values.java:19:29:19:31 | '*' | * |
+| constants/Values.java:91:37:91:45 | "a" + "b" | ab |
+| constants/Values.java:92:29:92:38 | ... + ... | abc |

java/ql/test/library-tests/constants/getStringValue.ql

@@ -0,0 +1,9 @@
+import semmle.code.java.Variable
+
+from Variable v, Expr init, RefType enclosing, string constant
+where
+  v.getInitializer() = init and
+  init.getEnclosingCallable().getDeclaringType() = enclosing and
+  enclosing.hasQualifiedName("constants", "Values") and
+  constant = init.(CompileTimeConstantExpr).getStringValue()
+select init, constant