Support ternary conditionals in Python backend

10 files changed, 201 insertions, 91 deletions

diff --git a/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java b/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
index b1947a8..0db2be6 100644
--- a/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
+++ b/src/main/java/org/zwobble/couscous/backends/python/PythonCodeGenerator.java
@@ -32,7 +32,9 @@ import org.zwobble.couscous.values.UnitValue;
 
 import static java.util.Arrays.asList;
 import static org.zwobble.couscous.backends.python.ast.PythonAssignmentNode.pythonAssignment;
+import static org.zwobble.couscous.backends.python.ast.PythonBooleanLiteralNode.pythonBooleanLiteral;
 import static org.zwobble.couscous.backends.python.ast.PythonClassNode.pythonClass;
+import static org.zwobble.couscous.backends.python.ast.PythonConditionalExpressionNode.pythonConditionalExpression;
 import static org.zwobble.couscous.backends.python.ast.PythonFunctionDefinitionNode.pythonFunctionDefinition;
 import static org.zwobble.couscous.backends.python.ast.PythonIntegerLiteralNode.pythonIntegerLiteral;
 import static org.zwobble.couscous.backends.python.ast.PythonModuleNode.pythonModule;
@@ -67,7 +69,7 @@ public class PythonCodeGenerator {
 
             @Override
             public PythonExpressionNode visit(BooleanValue value) {
-                throw new UnsupportedOperationException();
+                return pythonBooleanLiteral(value.getValue());
             }
 
             @Override
@@ -144,7 +146,10 @@ public class PythonCodeGenerator {
 
         @Override
         public PythonExpressionNode visit(TernaryConditionalNode ternaryConditional) {
-            throw new UnsupportedOperationException();
+            return pythonConditionalExpression(
+                generateExpression(ternaryConditional.getCondition()),
+                generateExpression(ternaryConditional.getIfTrue()),
+                generateExpression(ternaryConditional.getIfFalse()));
         }
 
         @Override
diff --git a/src/main/java/org/zwobble/couscous/backends/python/PythonSerializer.java b/src/main/java/org/zwobble/couscous/backends/python/PythonSerializer.java
index bc5fb19..728b71a 100644
--- a/src/main/java/org/zwobble/couscous/backends/python/PythonSerializer.java
+++ b/src/main/java/org/zwobble/couscous/backends/python/PythonSerializer.java
@@ -4,6 +4,8 @@ import org.zwobble.couscous.backends.python.ast.PythonAssignmentNode;
 import org.zwobble.couscous.backends.python.ast.PythonBlock;
 import org.zwobble.couscous.backends.python.ast.PythonBooleanLiteralNode;
 import org.zwobble.couscous.backends.python.ast.PythonClassNode;
+import org.zwobble.couscous.backends.python.ast.PythonConditionalExpressionNode;
+import org.zwobble.couscous.backends.python.ast.PythonExpressionNode;
 import org.zwobble.couscous.backends.python.ast.PythonFunctionDefinitionNode;
 import org.zwobble.couscous.backends.python.ast.PythonIntegerLiteralNode;
 import org.zwobble.couscous.backends.python.ast.PythonModuleNode;
@@ -62,6 +64,20 @@ public class PythonSerializer implements PythonNodeVisitor<Void> {
     }
 
     @Override
+    public Void visit(PythonConditionalExpressionNode conditional) {
+        writeParenthesised(conditional.getTrueValue());
+        writer.writeSpace();
+        writer.writeKeyword("if");
+        writer.writeSpace();
+        writeParenthesised(conditional.getCondition());
+        writer.writeSpace();
+        writer.writeKeyword("else");
+        writer.writeSpace();
+        writeParenthesised(conditional.getFalseValue());
+        return null;
+    }
+
+    @Override
     public Void visit(PythonReturnNode pythonReturn) {
         writer.startStatement();
         writer.writeKeyword("return");
@@ -119,6 +135,12 @@ public class PythonSerializer implements PythonNodeVisitor<Void> {
         return null;
     }
 
+    private void writeParenthesised(PythonExpressionNode expression) {
+        writer.writeSymbol("(");
+        write(expression);
+        writer.writeSymbol(")");
+    }
+
     private void writeArgumentNames(PythonFunctionDefinitionNode functionDefinition) {
         if (!functionDefinition.getArgumentNames().isEmpty()) {
             writer.writeIdentifier(functionDefinition.getArgumentNames().get(0));
diff --git a/src/main/java/org/zwobble/couscous/backends/python/ast/PythonConditionalExpressionNode.java b/src/main/java/org/zwobble/couscous/backends/python/ast/PythonConditionalExpressionNode.java
new file mode 100644
index 0000000..9fd406c
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/backends/python/ast/PythonConditionalExpressionNode.java
@@ -0,0 +1,17 @@
+package org.zwobble.couscous.backends.python.ast;
+
+import org.zwobble.couscous.backends.python.ast.visitors.PythonNodeVisitor;
+
+import lombok.Value;
+
+@Value(staticConstructor="pythonConditionalExpression")
+public class PythonConditionalExpressionNode implements PythonExpressionNode {
+    PythonExpressionNode condition;
+    PythonExpressionNode trueValue;
+    PythonExpressionNode falseValue;
+    
+    @Override
+    public <T> T accept(PythonNodeVisitor<T> visitor) {
+        return visitor.visit(this);
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/backends/python/ast/visitors/PythonNodeVisitor.java b/src/main/java/org/zwobble/couscous/backends/python/ast/visitors/PythonNodeVisitor.java
index f5cd04f..1f5b1a2 100644
--- a/src/main/java/org/zwobble/couscous/backends/python/ast/visitors/PythonNodeVisitor.java
+++ b/src/main/java/org/zwobble/couscous/backends/python/ast/visitors/PythonNodeVisitor.java
@@ -3,6 +3,7 @@ package org.zwobble.couscous.backends.python.ast.visitors;
 import org.zwobble.couscous.backends.python.ast.PythonAssignmentNode;
 import org.zwobble.couscous.backends.python.ast.PythonBooleanLiteralNode;
 import org.zwobble.couscous.backends.python.ast.PythonClassNode;
+import org.zwobble.couscous.backends.python.ast.PythonConditionalExpressionNode;
 import org.zwobble.couscous.backends.python.ast.PythonFunctionDefinitionNode;
 import org.zwobble.couscous.backends.python.ast.PythonIntegerLiteralNode;
 import org.zwobble.couscous.backends.python.ast.PythonModuleNode;
@@ -16,6 +17,7 @@ public interface PythonNodeVisitor<T> {
     T visit(PythonStringLiteralNode stringLiteral);
     T visit(PythonBooleanLiteralNode booleanLiteral);
     T visit(PythonVariableReferenceNode reference);
+    T visit(PythonConditionalExpressionNode conditional);
     
     T visit(PythonReturnNode pythonReturn);
     T visit(PythonPassNode pass);
diff --git a/src/test/java/org/zwobble/couscous/tests/BackendEvalTests.java b/src/test/java/org/zwobble/couscous/tests/BackendEvalTests.java
new file mode 100644
index 0000000..c4a3538
--- /dev/null
+++ b/src/test/java/org/zwobble/couscous/tests/BackendEvalTests.java
@@ -0,0 +1,28 @@
+package org.zwobble.couscous.tests;
+
+import org.junit.Test;
+import org.zwobble.couscous.ast.ExpressionNode;
+import org.zwobble.couscous.ast.TernaryConditionalNode;
+import org.zwobble.couscous.values.PrimitiveValue;
+
+import static org.junit.Assert.assertEquals;
+import static org.zwobble.couscous.ast.LiteralNode.literal;
+import static org.zwobble.couscous.values.PrimitiveValues.value;
+
+import lombok.val;
+
+public abstract class BackendEvalTests {
+    @Test
+    public void whenConditionIsTrueThenValueOfConditionalTernaryIsTrueBranch() {
+        val result = evalExpression(new TernaryConditionalNode(literal(true), literal("T"), literal("F")));
+        assertEquals(value("T"), result);
+    }
+    
+    @Test
+    public void whenConditionIsFalseThenValueOfConditionalTernaryIsFalseBranch() {
+        val result = evalExpression(new TernaryConditionalNode(literal(false), literal("T"), literal("F")));
+        assertEquals(value("F"), result);
+    }
+    
+    protected abstract PrimitiveValue evalExpression(ExpressionNode expression);
+}
diff --git a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerEvalTests.java b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerEvalTests.java
new file mode 100644
index 0000000..6f19eb3
--- /dev/null
+++ b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerEvalTests.java
@@ -0,0 +1,27 @@
+package org.zwobble.couscous.tests.backends.python;
+
+import org.zwobble.couscous.ast.ClassNode;
+import org.zwobble.couscous.ast.ExpressionNode;
+import org.zwobble.couscous.ast.MethodNode;
+import org.zwobble.couscous.ast.ReturnNode;
+import org.zwobble.couscous.tests.BackendEvalTests;
+import org.zwobble.couscous.values.PrimitiveValue;
+
+import com.google.common.collect.ImmutableList;
+
+import lombok.val;
+
+public class PythonCompilerEvalTests extends BackendEvalTests {
+    @Override
+    protected PrimitiveValue evalExpression(ExpressionNode expression) {
+        val runner = new PythonMethodRunner();
+        return runner.runMethod(
+            ClassNode.builder("Program")
+                .method(MethodNode.staticMethod("run")
+                    .statement(new ReturnNode(expression))
+                    .build())
+                .build(),
+            "run",
+            ImmutableList.of());
+    }
+}
diff --git a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerMethodTests.java b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerMethodTests.java
index 93c283a..6666ac4 100644
--- a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerMethodTests.java
+++ b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonCompilerMethodTests.java
@@ -1,84 +1,11 @@
 package org.zwobble.couscous.tests.backends.python;
 
-import java.io.IOException;
-import java.io.InputStream;
-import java.io.InputStreamReader;
-import java.nio.file.Files;
-import java.util.List;
-
-import org.zwobble.couscous.ast.ClassNode;
-import org.zwobble.couscous.backends.python.PythonCodeGenerator;
-import org.zwobble.couscous.backends.python.PythonCompiler;
-import org.zwobble.couscous.backends.python.PythonSerializer;
 import org.zwobble.couscous.tests.BackendMethodTests;
 import org.zwobble.couscous.tests.MethodRunner;
-import org.zwobble.couscous.values.PrimitiveValue;
-import org.zwobble.couscous.values.PrimitiveValues;
-
-import com.google.common.base.Charsets;
-import com.google.common.base.Joiner;
-import com.google.common.io.CharStreams;
-
-import static java.lang.Integer.parseInt;
-import static java.util.Arrays.asList;
-import static org.zwobble.couscous.tests.util.ExtraFiles.deleteRecursively;
-import static org.zwobble.couscous.values.PrimitiveValues.value;
-
-import lombok.SneakyThrows;
-import lombok.val;
 
 public class PythonCompilerMethodTests extends BackendMethodTests {
     @Override
     protected MethodRunner buildMethodRunner() {
-        return new MethodRunner() {
-            @Override
-            @SneakyThrows
-            public PrimitiveValue runMethod(
-                    ClassNode classNode,
-                    String methodName,
-                    List<PrimitiveValue> arguments) {
-                val compiler = new PythonCompiler();
-                val directoryPath = Files.createTempDirectory(null);
-                try {
-                    compiler.compile(asList(classNode), directoryPath);
-                    
-                    val argumentsString = Joiner.on(", ").join(arguments.stream()
-                        .map(PythonCodeGenerator::generateCode)
-                        .map(PythonSerializer::serialize)
-                        .iterator());
-                    
-                    val program = "from " + classNode.getName() + " import " + classNode.getLocalName() +
-                        ";print(repr(" + classNode.getLocalName() + "." + methodName + "(" + argumentsString + ")))";
-                    
-                    val process = new ProcessBuilder("python3.4", "-c", program)
-                        .directory(directoryPath.toFile())
-                        .start();
-                    val exitCode = process.waitFor();
-                    val output = readString(process.getInputStream()).trim();
-                    val stderrOutput = readString(process.getErrorStream());
-                    if (exitCode != 0) {
-                        throw new RuntimeException("stderr was: " + stderrOutput);
-                    } else {
-                        return readPrimitive(output);
-                    }
-                } finally {
-                    deleteRecursively(directoryPath.toFile());
-                }
-            }
-
-            private PrimitiveValue readPrimitive(String output) {
-                if (output.equals("None")) {
-                    return PrimitiveValues.UNIT;
-                } else if (output.startsWith("'")) {
-                    return value(output.substring(1, output.length() - 1));
-                } else {
-                    return value(parseInt(output));
-                }
-            }
-
-            private String readString(final InputStream stream) throws IOException {
-                return CharStreams.toString(new InputStreamReader(stream, Charsets.UTF_8));
-            }
-        };
+        return new PythonMethodRunner();
     }
 }
diff --git a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonMethodRunner.java b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonMethodRunner.java
new file mode 100644
index 0000000..fb0e880
--- /dev/null
+++ b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonMethodRunner.java
@@ -0,0 +1,78 @@
+package org.zwobble.couscous.tests.backends.python;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.file.Files;
+import java.util.List;
+
+import org.zwobble.couscous.ast.ClassNode;
+import org.zwobble.couscous.backends.python.PythonCodeGenerator;
+import org.zwobble.couscous.backends.python.PythonCompiler;
+import org.zwobble.couscous.backends.python.PythonSerializer;
+import org.zwobble.couscous.tests.MethodRunner;
+import org.zwobble.couscous.values.PrimitiveValue;
+import org.zwobble.couscous.values.PrimitiveValues;
+
+import com.google.common.base.Charsets;
+import com.google.common.base.Joiner;
+import com.google.common.io.CharStreams;
+
+import static java.lang.Integer.parseInt;
+import static java.util.Arrays.asList;
+import static org.zwobble.couscous.tests.util.ExtraFiles.deleteRecursively;
+import static org.zwobble.couscous.values.PrimitiveValues.value;
+
+import lombok.SneakyThrows;
+import lombok.val;
+
+public class PythonMethodRunner implements MethodRunner {
+    @Override
+    @SneakyThrows
+    public PrimitiveValue runMethod(
+            ClassNode classNode,
+            String methodName,
+            List<PrimitiveValue> arguments) {
+        val compiler = new PythonCompiler();
+        val directoryPath = Files.createTempDirectory(null);
+        try {
+            compiler.compile(asList(classNode), directoryPath);
+            
+            val argumentsString = Joiner.on(", ").join(arguments.stream()
+                .map(PythonCodeGenerator::generateCode)
+                .map(PythonSerializer::serialize)
+                .iterator());
+            
+            val program = "from " + classNode.getName() + " import " + classNode.getLocalName() +
+                ";print(repr(" + classNode.getLocalName() + "." + methodName + "(" + argumentsString + ")))";
+            
+            val process = new ProcessBuilder("python3.4", "-c", program)
+                .directory(directoryPath.toFile())
+                .start();
+            val exitCode = process.waitFor();
+            val output = readString(process.getInputStream()).trim();
+            val stderrOutput = readString(process.getErrorStream());
+            if (exitCode != 0) {
+                throw new RuntimeException("stderr was: " + stderrOutput);
+            } else {
+                return readPrimitive(output);
+            }
+        } finally {
+            deleteRecursively(directoryPath.toFile());
+        }
+    }
+
+    private PrimitiveValue readPrimitive(String output) {
+        if (output.equals("None")) {
+            return PrimitiveValues.UNIT;
+        } else if (output.startsWith("'")) {
+            return value(output.substring(1, output.length() - 1));
+        } else {
+            return value(parseInt(output));
+        }
+    }
+
+    private String readString(final InputStream stream) throws IOException {
+        return CharStreams.toString(new InputStreamReader(stream, Charsets.UTF_8));
+    }
+}
diff --git a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonSerializerTests.java b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonSerializerTests.java
index 2835034..60aed36 100644
--- a/src/test/java/org/zwobble/couscous/tests/backends/python/PythonSerializerTests.java
+++ b/src/test/java/org/zwobble/couscous/tests/backends/python/PythonSerializerTests.java
@@ -9,6 +9,7 @@ import static org.junit.Assert.assertEquals;
 import static org.zwobble.couscous.backends.python.PythonSerializer.serialize;
 import static org.zwobble.couscous.backends.python.ast.PythonAssignmentNode.pythonAssignment;
 import static org.zwobble.couscous.backends.python.ast.PythonBooleanLiteralNode.pythonBooleanLiteral;
+import static org.zwobble.couscous.backends.python.ast.PythonConditionalExpressionNode.pythonConditionalExpression;
 import static org.zwobble.couscous.backends.python.ast.PythonIntegerLiteralNode.pythonIntegerLiteral;
 import static org.zwobble.couscous.backends.python.ast.PythonModuleNode.pythonModule;
 import static org.zwobble.couscous.backends.python.ast.PythonPassNode.PASS;
@@ -44,6 +45,15 @@ public class PythonSerializerTests {
     }
     
     @Test
+    public void conditionalExpressionIsSerializedUsingParens() {
+        assertEquals("(1) if (True) else (2)", serialize(
+            pythonConditionalExpression(
+                pythonBooleanLiteral(true),
+                pythonIntegerLiteral(1),
+                pythonIntegerLiteral(2))));
+    }
+    
+    @Test
     public void returnKeywordIsUsedForReturns() {
         val output = serialize(pythonReturn(pythonIntegerLiteral(42)));
         assertEquals("return 42\n", output);
diff --git a/src/test/java/org/zwobble/couscous/tests/interpreter/EvaluatorTests.java b/src/test/java/org/zwobble/couscous/tests/interpreter/EvaluatorTests.java
index 40cdf8f..0a2a947 100644
--- a/src/test/java/org/zwobble/couscous/tests/interpreter/EvaluatorTests.java
+++ b/src/test/java/org/zwobble/couscous/tests/interpreter/EvaluatorTests.java
@@ -4,6 +4,7 @@ import org.junit.Test;
 import org.zwobble.couscous.JavaProject;
 import org.zwobble.couscous.MapBackedProject;
 import org.zwobble.couscous.ast.ClassNode;
+import org.zwobble.couscous.ast.ExpressionNode;
 import org.zwobble.couscous.ast.MethodNode;
 import org.zwobble.couscous.ast.ReturnNode;
 import org.zwobble.couscous.ast.TernaryConditionalNode;
@@ -16,7 +17,9 @@ import org.zwobble.couscous.interpreter.WrongNumberOfArguments;
 import org.zwobble.couscous.interpreter.values.ConcreteType;
 import org.zwobble.couscous.interpreter.values.IntegerInterpreterValue;
 import org.zwobble.couscous.interpreter.values.StringInterpreterValue;
+import org.zwobble.couscous.tests.BackendEvalTests;
 import org.zwobble.couscous.values.IntegerValue;
+import org.zwobble.couscous.values.PrimitiveValue;
 import org.zwobble.couscous.values.StringValue;
 
 import com.google.common.collect.ImmutableMap;
@@ -34,7 +37,7 @@ import static org.zwobble.couscous.tests.util.ExtraAsserts.assertThrows;
 
 import lombok.val;
 
-public class EvaluatorTests {
+public class EvaluatorTests extends BackendEvalTests {
     @Test
     public void valueOfAssignmentExpressionIsNewValue() {
         val arg = formalArg(var(42, "x", StringValue.REF));
@@ -46,20 +49,6 @@ public class EvaluatorTests {
     }
     
     @Test
-    public void whenConditionIsTrueThenValueOfConditionalTernaryIsTrueBranch() {
-        val result = eval(emptyEnvironment(),
-            new TernaryConditionalNode(literal(true), literal("T"), literal("F")));
-        assertEquals(new StringInterpreterValue("T"), result);
-    }
-    
-    @Test
-    public void whenConditionIsFalseThenValueOfConditionalTernaryIsFalseBranch() {
-        val result = eval(emptyEnvironment(),
-            new TernaryConditionalNode(literal(false), literal("T"), literal("F")));
-        assertEquals(new StringInterpreterValue("F"), result);
-    }
-    
-    @Test
     public void errorIfConditionIsNotBoolean() {
         val exception = assertThrows(ConditionMustBeBoolean.class,
             () -> eval(emptyEnvironment(),
@@ -134,4 +123,9 @@ public class EvaluatorTests {
             JavaProject.builder().build(),
             ImmutableMap.of());
     }
+
+    @Override
+    protected PrimitiveValue evalExpression(ExpressionNode expression) {
+        return eval(emptyEnvironment(), expression).toPrimitiveValue().get();
+    }
 }