[2/x] Implement joda to java time migration recipe (#582)

* [2/x] Implement joda to java time migration recipe

* Update src/test/java/org/openrewrite/java/migrate/joda/JodaTimeScannerTest.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/test/java/org/openrewrite/java/migrate/joda/JodaTimeScannerTest.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/main/java/org/openrewrite/java/migrate/joda/JodaTimeFlowSpec.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/main/java/org/openrewrite/java/migrate/joda/JodaTimeScanner.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/main/java/org/openrewrite/java/migrate/joda/SafeCheckMarker.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/test/java/org/openrewrite/java/migrate/joda/JodaTimeFlowSpecTest.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/test/java/org/openrewrite/java/migrate/joda/JodaTimeFlowSpecTest.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/main/java/org/openrewrite/java/migrate/joda/templates/TimeClassMap.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Update src/main/java/org/openrewrite/java/migrate/joda/templates/AbstractInstantTemplates.java

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* github suggestion

* github auto commit mess

* Apply suggestions from code review

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

* Adopt AtomicBoolean

* Apply formatter

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Tim te Beek <timtebeek@gmail.com>
Co-authored-by: Tim te Beek <tim@moderne.io>

src/main/java/org/openrewrite/java/migrate/joda/JodaTimeFlowSpec.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2024 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.joda;
+
+import lombok.NonNull;
+import org.openrewrite.analysis.dataflow.DataFlowNode;
+import org.openrewrite.analysis.dataflow.DataFlowSpec;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+
+import static org.openrewrite.java.migrate.joda.templates.TimeClassNames.JODA_CLASS_PATTERN;
+
+public class JodaTimeFlowSpec extends DataFlowSpec {
+
+    @Override
+    public boolean isSource(@NonNull DataFlowNode srcNode) {
+        Object value = srcNode.getCursor().getParentTreeCursor().getValue();
+
+        if (value instanceof J.Assignment && ((J.Assignment) value).getVariable() instanceof J.Identifier) {
+            return isJodaType(((J.Assignment) value).getVariable().getType());
+        }
+
+        if (value instanceof J.VariableDeclarations.NamedVariable) {
+            return isJodaType(((J.VariableDeclarations.NamedVariable) value).getType());
+        }
+        return false;
+    }
+
+    @Override
+    public boolean isSink(@NonNull DataFlowNode sinkNode) {
+        Object value = sinkNode.getCursor().getValue();
+        Object parent = sinkNode.getCursor().getParentTreeCursor().getValue();
+        if (parent instanceof J.MethodInvocation) {
+            J.MethodInvocation method = (J.MethodInvocation) parent;
+            return (method.getSelect() != null && method.getSelect().equals(value)) ||
+                   method.getArguments().stream().anyMatch(a -> a.equals(value));
+        }
+        return parent instanceof J.VariableDeclarations.NamedVariable ||
+               parent instanceof J.NewClass ||
+               parent instanceof J.Assignment ||
+               parent instanceof J.Return;
+    }
+
+    static boolean isJodaType(JavaType type) {
+        if (!(type instanceof JavaType.Class)) {
+            return false;
+        }
+        return type.isAssignableFrom(JODA_CLASS_PATTERN);
+    }
+}

src/main/java/org/openrewrite/java/migrate/joda/JodaTimeScanner.java

@@ -0,0 +1,281 @@
+/*
+ * Copyright 2024 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate.joda;
+
+import fj.data.Option;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+import lombok.Value;
+import org.openrewrite.Cursor;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.analysis.dataflow.Dataflow;
+import org.openrewrite.analysis.dataflow.analysis.SinkFlowSummary;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.J.VariableDeclarations.NamedVariable;
+import org.openrewrite.java.tree.JavaType;
+
+import java.util.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static org.openrewrite.java.migrate.joda.templates.TimeClassNames.JODA_CLASS_PATTERN;
+
+public class JodaTimeScanner extends JavaIsoVisitor<ExecutionContext> {
+
+    @Getter
+    private final Set<NamedVariable> unsafeVars = new HashSet<>();
+
+    private final LinkedList<VariablesInScope> scopes = new LinkedList<>();
+
+    private final Map<NamedVariable, Set<NamedVariable>> varDependencies = new HashMap<>();
+
+    @Override
+    public J.CompilationUnit visitCompilationUnit(J.CompilationUnit cu, ExecutionContext ctx) {
+        cu = super.visitCompilationUnit(cu, ctx);
+        Set<NamedVariable> allReachable = new HashSet<>();
+        for (NamedVariable var : unsafeVars) {
+            dfs(var, allReachable);
+        }
+        unsafeVars.addAll(allReachable);
+        return cu;
+    }
+
+    @Override
+    public J.Block visitBlock(J.Block block, ExecutionContext ctx) {
+        scopes.push(new VariablesInScope(getCursor()));
+        J.Block b = super.visitBlock(block, ctx);
+        scopes.pop();
+        return b;
+    }
+
+    @Override
+    public NamedVariable visitVariable(NamedVariable variable, ExecutionContext ctx) {
+        assert !scopes.isEmpty();
+        scopes.peek().variables.add(variable);
+        if (!variable.getType().isAssignableFrom(JODA_CLASS_PATTERN)) {
+            return variable;
+        }
+        // TODO: handle class variables && method parameters
+        if (!isLocalVar(variable)) {
+            unsafeVars.add(variable);
+            return variable;
+        }
+        variable = super.visitVariable(variable, ctx);
+
+        if (!variable.getType().isAssignableFrom(JODA_CLASS_PATTERN) || variable.getInitializer() == null) {
+            return variable;
+        }
+        List<Expression> sinks = findSinks(variable.getInitializer());
+        assert !scopes.isEmpty();
+        Cursor currentScope = scopes.peek().getScope();
+        J.Block block = currentScope.getValue();
+        new AddSafeCheckMarker(sinks).visit(block, ctx, currentScope.getParent());
+        processMarkersOnExpression(sinks, variable);
+        return variable;
+    }
+
+    @Override
+    public J.Assignment visitAssignment(J.Assignment assignment, ExecutionContext ctx) {
+        Expression var = assignment.getVariable();
+        // not joda expr or not local variable
+        if (!isJodaExpr(var) || !(var instanceof J.Identifier)) {
+            return assignment;
+        }
+        J.Identifier ident = (J.Identifier) var;
+        Optional<NamedVariable> mayBeVar = findVarInScope(ident.getSimpleName());
+        if (!mayBeVar.isPresent()) {
+            return assignment;
+        }
+        NamedVariable variable = mayBeVar.get();
+        Cursor varScope = findScope(variable);
+        List<Expression> sinks = findSinks(assignment.getAssignment());
+        new AddSafeCheckMarker(sinks).visit(varScope.getValue(), ctx, varScope.getParent());
+        processMarkersOnExpression(sinks, variable);
+        return assignment;
+    }
+
+    private void processMarkersOnExpression(List<Expression> expressions, NamedVariable var) {
+        for (Expression expr : expressions) {
+            Optional<SafeCheckMarker> mayBeMarker = expr.getMarkers().findFirst(SafeCheckMarker.class);
+            if (!mayBeMarker.isPresent()) {
+                continue;
+            }
+            SafeCheckMarker marker = mayBeMarker.get();
+            if (!marker.isSafe()) {
+                unsafeVars.add(var);
+            }
+            if (!marker.getReferences().isEmpty()) {
+                varDependencies.compute(var, (k, v) -> v == null ? new HashSet<>() : v).addAll(marker.getReferences());
+                for (NamedVariable ref : marker.getReferences()) {
+                    varDependencies.compute(ref, (k, v) -> v == null ? new HashSet<>() : v).add(var);
+                }
+            }
+        }
+    }
+
+    private boolean isJodaExpr(Expression expression) {
+        return expression.getType() != null && expression.getType().isAssignableFrom(JODA_CLASS_PATTERN);
+    }
+
+    private List<Expression> findSinks(Expression expr) {
+        Cursor cursor = new Cursor(getCursor(), expr);
+        Option<SinkFlowSummary> mayBeSinks = Dataflow.startingAt(cursor).findSinks(new JodaTimeFlowSpec());
+        if (mayBeSinks.isNone()) {
+            return Collections.emptyList();
+        }
+        return mayBeSinks.some().getExpressionSinks();
+    }
+
+    private boolean isLocalVar(NamedVariable variable) {
+        if (!(variable.getVariableType().getOwner() instanceof JavaType.Method)) {
+            return false;
+        }
+        J j = getCursor().dropParentUntil(t -> t instanceof J.Block || t instanceof J.MethodDeclaration).getValue();
+        return j instanceof J.Block;
+    }
+
+    // Returns the variable in the closest scope
+    private Optional<NamedVariable> findVarInScope(String varName) {
+        for (VariablesInScope scope : scopes) {
+            for (NamedVariable var : scope.variables) {
+                if (var.getSimpleName().equals(varName)) {
+                    return Optional.of(var);
+                }
+            }
+        }
+        return Optional.empty();
+    }
+
+    private Cursor findScope(NamedVariable variable) {
+        for (VariablesInScope scope : scopes) {
+            if (scope.variables.contains(variable)) {
+                return scope.scope;
+            }
+        }
+        return null;
+    }
+
+    private void dfs(NamedVariable root, Set<NamedVariable> visited) {
+        if (visited.contains(root)) {
+            return;
+        }
+        visited.add(root);
+        for (NamedVariable dep : varDependencies.getOrDefault(root, Collections.emptySet())) {
+            dfs(dep, visited);
+        }
+    }
+
+    @Value
+    private static class VariablesInScope {
+        Cursor scope;
+        Set<NamedVariable> variables;
+
+        public VariablesInScope(Cursor scope) {
+            this.scope = scope;
+            this.variables = new HashSet<>();
+        }
+    }
+
+    @RequiredArgsConstructor
+    private class AddSafeCheckMarker extends JavaIsoVisitor<ExecutionContext> {
+
+        @NonNull
+        private List<Expression> expressions;
+
+        @Override
+        public Expression visitExpression(Expression expression, ExecutionContext ctx) {
+            int index = expressions.indexOf(expression);
+            if (index == -1) {
+                return super.visitExpression(expression, ctx);
+            }
+            Expression withMarker = expression.withMarkers(expression.getMarkers().addIfAbsent(getMarker(expression, ctx)));
+            expressions.set(index, withMarker);
+            return withMarker;
+        }
+
+        private SafeCheckMarker getMarker(Expression expr, ExecutionContext ctx) {
+            Optional<SafeCheckMarker> mayBeMarker = expr.getMarkers().findFirst(SafeCheckMarker.class);
+            if (mayBeMarker.isPresent()) {
+                return mayBeMarker.get();
+            }
+
+            Cursor boundary = findBoundaryCursorForJodaExpr();
+            boolean isSafe = true;
+            // TODO: handle return statement
+            if (boundary.getParentTreeCursor().getValue() instanceof J.Return) {
+                isSafe = false;
+            }
+            Expression boundaryExpr = boundary.getValue();
+            J j = new JodaTimeVisitor(true).visit(boundaryExpr, ctx, boundary.getParentTreeCursor());
+            Set<NamedVariable> referencedVars = new HashSet<>();
+            new FindVarReferences().visit(expr, referencedVars, getCursor().getParentTreeCursor());
+            AtomicBoolean hasJodaType = new AtomicBoolean();
+            new HasJodaType().visit(j, hasJodaType);
+            isSafe = isSafe && !hasJodaType.get() && !referencedVars.contains(null);
+            referencedVars.remove(null);
+            return new SafeCheckMarker(UUID.randomUUID(), isSafe, referencedVars);
+        }
+
+        /**
+         * Traverses the cursor to find the first non-Joda expression in the path.
+         * If no non-Joda expression is found, it returns the cursor pointing
+         * to the last Joda expression whose parent is not an Expression.
+         */
+        private Cursor findBoundaryCursorForJodaExpr() {
+            Cursor cursor = getCursor();
+            while (cursor.getValue() instanceof Expression && isJodaExpr(cursor.getValue())) {
+                Cursor parent = cursor.getParentTreeCursor();
+                if (parent.getValue() instanceof J && !(parent.getValue() instanceof Expression)) {
+                    return cursor;
+                }
+                cursor = parent;
+            }
+            return cursor;
+        }
+    }
+
+    private class FindVarReferences extends JavaIsoVisitor<Set<NamedVariable>> {
+
+        @Override
+        public J.Identifier visitIdentifier(J.Identifier ident, Set<NamedVariable> vars) {
+            if (!isJodaExpr(ident) || ident.getFieldType() == null) {
+                return ident;
+            }
+            if (ident.getFieldType().getOwner() instanceof JavaType.Class) {
+                vars.add(null); // class variable not supported yet.
+            }
+
+            // find variable in the closest scope
+            findVarInScope(ident.getSimpleName()).ifPresent(vars::add);
+            return ident;
+        }
+    }
+
+    private static class HasJodaType extends JavaIsoVisitor<AtomicBoolean> {
+        @Override
+        public Expression visitExpression(Expression expression, AtomicBoolean hasJodaType) {
+            if (hasJodaType.get()) {
+                return expression;
+            }
+            if (expression.getType() != null && expression.getType().isAssignableFrom(JODA_CLASS_PATTERN)) {
+                hasJodaType.set(true);
+            }
+            return super.visitExpression(expression, hasJodaType);
+        }
+    }
+}