SONARPY-628 Fix FP on S1226 and S1481 with raw f-strings (#656)

Author: pynicolas

python-checks/src/test/resources/checks/unusedLocalVariable.py

@@ -28,6 +28,8 @@ def string_interpolation():
     foo(F'{value5} foo')
     value6 = ''
     print(f"{'}' + value6}")
+    value7 = ''
+    printf(rf'{value7}')
     return f'{value1}, {2*value2}, value3bis, value4'
 
 def function_with_lambdas():

python-frontend/src/main/java/org/sonar/python/tree/StringElementImpl.java

@@ -87,7 +87,7 @@ public String trimmedQuotesValue() {
 
   @Override
   public String prefix() {
-    return value.substring(0, value.length() - removePrefix(value).length());
+    return value.substring(0, prefixLength(value));
   }
 
   @Override
@@ -97,7 +97,8 @@ public boolean isTripleQuoted() {
 
   @Override
   public boolean isInterpolated() {
-    return prefix().equalsIgnoreCase("F");
+    String prefix = prefix();
+    return prefix.indexOf('f') >= 0 || prefix.indexOf('F') >= 0;
   }
 
   @Override

python-frontend/src/test/java/org/sonar/python/tree/StringElementImplTest.java

@@ -0,0 +1,43 @@
+/*
+ * SonarQube Python Plugin
+ * Copyright (C) 2011-2020 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package org.sonar.python.tree;
+
+import org.junit.Test;
+import org.sonar.plugins.python.api.tree.StringElement;
+import org.sonar.plugins.python.api.tree.StringLiteral;
+import org.sonar.python.PythonTestUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StringElementImplTest {
+
+  @Test
+  public void isInterpolated() {
+    assertThat(stringElement("'abc'").isInterpolated()).isFalse();
+    assertThat(stringElement("f'abc'").isInterpolated()).isTrue();
+    assertThat(stringElement("F'abc'").isInterpolated()).isTrue();
+    assertThat(stringElement("r'abc'").isInterpolated()).isFalse();
+    assertThat(stringElement("rf'abc'").isInterpolated()).isTrue();
+  }
+
+  private StringElement stringElement(String code) {
+    return ((StringLiteral) PythonTestUtils.lastExpression(code)).stringElements().get(0);
+  }
+}