SONARPY-918 Match / case statement: as patterns

Author: andreaguarino

python-frontend/src/main/java/org/sonar/plugins/python/api/tree/AsPattern.java

@@ -0,0 +1,35 @@
+/*
+ * SonarQube Python Plugin
+ * Copyright (C) 2011-2021 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.plugins.python.api.tree;
+
+
+/**
+ * As pattern
+ *
+ * <pre>{@link #pattern()} as {@link #alias()}</pre>
+ *
+ * See https://docs.python.org/3/reference/compound_stmts.html#as-patterns
+ */
+public interface AsPattern extends Pattern {
+
+  Pattern pattern();
+
+  Name alias();
+}

python-frontend/src/main/java/org/sonar/plugins/python/api/tree/BaseTreeVisitor.java

@@ -490,6 +490,12 @@ public void visitLiteralPattern(LiteralPattern literalPattern) {
     // noop
   }
 
+  @Override
+  public void visitAsPattern(AsPattern asPattern) {
+    scan(asPattern.pattern());
+    scan(asPattern.alias());
+  }
+
   @Override
   public void visitGuard(Guard guard) {
     scan(guard.condition());

python-frontend/src/main/java/org/sonar/plugins/python/api/tree/Tree.java

@@ -42,6 +42,8 @@ public interface Tree {
   enum Kind {
     ALIASED_NAME(AliasedName.class),
 
+    AS_PATTERN(AsPattern.class),
+
     REGULAR_ARGUMENT(RegularArgument.class),
 
     ARG_LIST(ArgList.class),

python-frontend/src/main/java/org/sonar/plugins/python/api/tree/TreeVisitor.java

@@ -179,5 +179,7 @@ public interface TreeVisitor {
 
   void visitLiteralPattern(LiteralPattern literalPattern);
 
+  void visitAsPattern(AsPattern asPattern);
+
   void visitGuard(Guard guard);
 }

python-frontend/src/main/java/org/sonar/python/api/PythonGrammar.java

@@ -155,7 +155,10 @@ public enum PythonGrammar implements GrammarRuleKey {
   GUARD,
 
   PATTERN,
+  AS_PATTERN,
+  CLOSED_PATTERN,
   LITERAL_PATTERN,
+  CAPTURE_PATTERN,
 
   SIGNED_NUMBER,
   COMPLEX_NUMBER,
@@ -455,8 +458,10 @@ public static void compoundStatements(LexerfulGrammarBuilder b) {
     b.rule(CASE_BLOCK).is("case", PATTERN, b.optional(GUARD), ":", SUITE);
     b.rule(GUARD).is("if", NAMED_EXPR_TEST);
 
-    // TODO: this should be either OR_PATTERN or AS_PATTERN
-    b.rule(PATTERN).is(LITERAL_PATTERN);
+    b.rule(PATTERN).is(b.firstOf(AS_PATTERN, CLOSED_PATTERN));
+    b.rule(CLOSED_PATTERN).is(LITERAL_PATTERN);
+    b.rule(AS_PATTERN).is(CLOSED_PATTERN, "as", CAPTURE_PATTERN);
+    b.rule(CAPTURE_PATTERN).is(NAME);
 
     b.rule(LITERAL_PATTERN).is(b.firstOf(
       COMPLEX_NUMBER,

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

@@ -0,0 +1,66 @@
+/*
+ * SonarQube Python Plugin
+ * Copyright (C) 2011-2021 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 java.util.Arrays;
+import java.util.List;
+import org.sonar.plugins.python.api.tree.AsPattern;
+import org.sonar.plugins.python.api.tree.Name;
+import org.sonar.plugins.python.api.tree.Pattern;
+import org.sonar.plugins.python.api.tree.Token;
+import org.sonar.plugins.python.api.tree.Tree;
+import org.sonar.plugins.python.api.tree.TreeVisitor;
+
+public class AsPatternImpl extends PyTree implements AsPattern {
+  private final Pattern pattern;
+  private final Token asKeyword;
+  private final Name alias;
+
+  public AsPatternImpl(Pattern pattern, Token asKeyword, Name alias) {
+    this.pattern = pattern;
+    this.asKeyword = asKeyword;
+    this.alias = alias;
+  }
+
+  @Override
+  public Pattern pattern() {
+    return pattern;
+  }
+
+  @Override
+  public Name alias() {
+    return alias;
+  }
+
+  @Override
+  public void accept(TreeVisitor visitor) {
+    visitor.visitAsPattern(this);
+  }
+
+  @Override
+  public Kind getKind() {
+    return Kind.AS_PATTERN;
+  }
+
+  @Override
+  List<Tree> computeChildren() {
+    return Arrays.asList(pattern, asKeyword, alias);
+  }
+}

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

@@ -34,6 +34,7 @@
 import org.sonar.plugins.python.api.tree.AnyParameter;
 import org.sonar.plugins.python.api.tree.ArgList;
 import org.sonar.plugins.python.api.tree.Argument;
+import org.sonar.plugins.python.api.tree.AsPattern;
 import org.sonar.plugins.python.api.tree.AssertStatement;
 import org.sonar.plugins.python.api.tree.AssignmentExpression;
 import org.sonar.plugins.python.api.tree.AssignmentStatement;
@@ -804,7 +805,7 @@ public MatchStatement matchStatement(AstNode matchStmt) {
 
   public CaseBlock caseBlock(AstNode caseBlock) {
     Token caseKeyword = toPyToken(caseBlock.getTokens().get(0));
-    Pattern pattern = pattern(caseBlock.getFirstChild(PythonGrammar.PATTERN));
+    Pattern pattern = pattern(caseBlock.getFirstChild(PythonGrammar.PATTERN).getFirstChild());
     Guard guard = null;
     AstNode guardNode = caseBlock.getFirstChild(PythonGrammar.GUARD);
     if (guardNode != null) {
@@ -824,7 +825,22 @@ public Guard guard(AstNode guardNode) {
 
   private static Pattern pattern(AstNode pattern) {
     // TODO: consider OR Patterns and other kind of patterns
-    AstNode literalPattern = pattern.getFirstChild(PythonGrammar.LITERAL_PATTERN);
+    if (pattern.is(PythonGrammar.CLOSED_PATTERN)) {
+      return literalPattern(pattern.getFirstChild());
+    } else if (pattern.is(PythonGrammar.AS_PATTERN)) {
+      return asPattern(pattern);
+    }
+    throw new IllegalStateException(String.format("Pattern %s not recognized.", pattern.getName()));
+  }
+
+  private static AsPattern asPattern(AstNode asPattern) {
+    Pattern pattern = literalPattern(asPattern.getFirstChild(PythonGrammar.CLOSED_PATTERN).getFirstChild());
+    Token asKeyword = toPyToken(asPattern.getFirstChild(PythonKeyword.AS).getToken());
+    Name alias = name(asPattern.getFirstChild(PythonGrammar.CAPTURE_PATTERN).getFirstChild());
+    return new AsPatternImpl(pattern, asKeyword, alias);
+  }
+
+  private static LiteralPattern literalPattern(AstNode literalPattern) {
     LiteralPattern.LiteralKind literalKind;
     if (literalPattern.hasDirectChildren(PythonGrammar.COMPLEX_NUMBER, PythonGrammar.SIGNED_NUMBER)) {
       literalKind = LiteralPattern.LiteralKind.NUMBER;

python-frontend/src/test/java/org/sonar/python/parser/compound/statements/CasePatternsTest.java

@@ -66,4 +66,11 @@ public void complex_numbers() {
       .matches("3 + 4j")
       .matches("42j");
   }
+
+  @Test
+  public void as_patterns() {
+    assertThat(p)
+      .matches("'foo' as x")
+      .notMatches("'foo' as x as y");
+  }
 }

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

@@ -20,6 +20,7 @@
 package org.sonar.python.tree;
 
 import org.junit.Test;
+import org.sonar.plugins.python.api.tree.AsPattern;
 import org.sonar.plugins.python.api.tree.CaseBlock;
 import org.sonar.plugins.python.api.tree.Expression;
 import org.sonar.plugins.python.api.tree.Guard;
@@ -146,4 +147,14 @@ public void literal_patterns() {
     assertThat(literalPattern.literalKind()).isEqualTo(LiteralPattern.LiteralKind.BOOLEAN);
     assertThat(literalPattern.valueAsString()).isEqualTo("False");
   }
+
+  @Test
+  public void as_pattern() {
+    setRootRule(PythonGrammar.CASE_BLOCK);
+    CaseBlock caseBlock = parse("case \"foo\" as x: ...", treeMaker::caseBlock);
+    AsPattern asPattern = (AsPattern) caseBlock.pattern();
+    assertThat(asPattern.pattern()).isInstanceOf(LiteralPattern.class);
+    assertThat(asPattern.alias().name()).isEqualTo("x");
+    assertThat(asPattern.children()).extracting(Tree::getKind).containsExactly(Tree.Kind.LITERAL_PATTERN, Tree.Kind.TOKEN, Tree.Kind.NAME);
+  }
 }