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/*
* Copyright 2020 The Error Prone Authors.
*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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 com.google.errorprone.bugpatterns.flogger;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.fixes.SuggestedFixes.addModifiers;
import static com.google.errorprone.fixes.SuggestedFixes.removeModifiers;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
import static com.google.errorprone.util.ASTHelpers.isStatic;
import static javax.lang.model.element.Modifier.FINAL;
import static javax.lang.model.element.Modifier.PRIVATE;
import static javax.lang.model.element.Modifier.PROTECTED;
import static javax.lang.model.element.Modifier.PUBLIC;
import static javax.lang.model.element.Modifier.STATIC;
import com.google.common.base.Joiner;
import com.google.common.base.Verify;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.LinkType;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker;
import com.google.errorprone.bugpatterns.BugChecker.IdentifierTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MemberSelectTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.fixes.SuggestedFixes.AdditionPosition;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.matchers.Matchers;
import com.google.errorprone.suppliers.Supplier;
import com.google.errorprone.suppliers.Suppliers;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.ModifiersTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreePath;
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Symbol.VarSymbol;
import com.sun.tools.javac.code.Type;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import javax.inject.Inject;
import javax.lang.model.element.Modifier;
import javax.lang.model.element.NestingKind;
/** Ensures that class-level FluentLogger objects are private static final. */
@BugPattern(
summary =
"FluentLogger.forEnclosingClass should always be saved to a private static final field.",
link = "https://google.github.io/flogger/best_practice#modifiers",
linkType = LinkType.CUSTOM,
severity = WARNING)
public final class FloggerRequiredModifiers extends BugChecker
implements MethodInvocationTreeMatcher,
IdentifierTreeMatcher,
MemberSelectTreeMatcher,
VariableTreeMatcher {
private static final String GOOGLE_LOGGER = "com.google.common.flogger.FluentLogger";
private static final Supplier LOGGER_TYPE = Suppliers.typeFromString(GOOGLE_LOGGER);
private static final Matcher INIT_LOGGER =
staticMethod().onClass(LOGGER_TYPE).named("forEnclosingClass").withNoParameters();
private static final ImmutableList EXPECTED_MODIFIERS =
ImmutableList.of(Modifier.PRIVATE, STATIC, FINAL);
/** A list of names we could give to new fields of type Logger, in descending preference order. */
private static final ImmutableList REASONABLE_LOGGER_NAMES =
ImmutableList.of("logger", "flogger", "googleLogger", "myLogger");
private static final String NESTED_LOGGER_CLASSNAME = "Private";
private static final String NESTED_LOGGER_FIELDNAME = "logger";
private static final String NESTED_LOGGER_DEFINITION =
Joiner.on('\n')
.join(
"/** Do not use. Exists only to hide implementation details of this interface. */",
String.format("public static final class %s {", NESTED_LOGGER_CLASSNAME),
String.format(" private %s() {}", NESTED_LOGGER_CLASSNAME),
String.format(
" private static final FluentLogger %s = FluentLogger.forEnclosingClass();",
NESTED_LOGGER_FIELDNAME),
"}");
private final Map localLogger = new HashMap<>();
private static final Matcher CONTAINS_INIT_LOGGER =
Matchers.contains(ExpressionTree.class, INIT_LOGGER);
@Inject
FloggerRequiredModifiers() {}
@Override
public Description matchVariable(VariableTree tree, VisitorState state) {
Type loggerType = LOGGER_TYPE.get(state);
if (!ASTHelpers.isSameType(loggerType, ASTHelpers.getType(tree), state)) {
return NO_MATCH;
}
VarSymbol sym = ASTHelpers.getSymbol(tree);
if (!(sym.owner instanceof ClassSymbol)) {
return NO_MATCH;
}
ExpressionTree initializer = tree.getInitializer();
// Static fields with no initializer, or fields initialized to a constant FluentLogger
if (initializer == null
? sym.isStatic()
: isConstantLogger(initializer, (ClassSymbol) sym.owner, state)
&& !sym.owner.isInterface()) {
return fixModifier(tree, (ClassTree) state.getPath().getParentPath().getLeaf(), state);
}
return NO_MATCH;
}
private static boolean isConstantLogger(
ExpressionTree initializer, ClassSymbol owner, VisitorState state) {
if (initializer instanceof MethodInvocationTree) {
Type loggerType = LOGGER_TYPE.get(state);
MethodInvocationTree method = (MethodInvocationTree) initializer;
MethodSymbol methodSym = ASTHelpers.getSymbol(method);
if (methodSym.isStatic()
&& methodSym.owner.equals(owner)
&& ASTHelpers.isSameType(loggerType, methodSym.getReturnType(), state)) {
return true;
}
// Fall through to search for FluentLogger.forEnclosingClass()
}
return CONTAINS_INIT_LOGGER.matches(initializer, state);
}
@Override
public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
if (!INIT_LOGGER.matches(tree, state)) {
return NO_MATCH;
}
Type loggerType = LOGGER_TYPE.get(state);
if (loggerType == null) {
return NO_MATCH;
}
// An expression should always be inside a method or a variable (initializer blocks count as
// a method), but just in case we use class as a final backstop.
TreePath owner =
state.findPathToEnclosing(ClassTree.class, MethodTree.class, VariableTree.class);
Tree parent = owner.getLeaf();
Tree grandparent = owner.getParentPath().getLeaf();
boolean isLoggerField =
parent instanceof VariableTree
&& grandparent instanceof ClassTree
&& ASTHelpers.isSameType(loggerType, ASTHelpers.getType(parent), state);
if (isLoggerField) {
// Declared as a class member - matchVariable will already have fixed the modifiers, and we
// allow calls to forEnclosingClass() in initializer context, so we can just quit here
return NO_MATCH;
}
// See if they're defining a static method that produces a FluentLogger. If so, we assume they
// are using it to initialize their FluentLogger instance, and we don't stop them from calling
// FluentLogger.forEnclosingClass() inside the method.
MethodTree owningMethod = state.findEnclosing(MethodTree.class);
if (owningMethod != null) {
MethodSymbol methodSym = ASTHelpers.getSymbol(owningMethod);
Type returnType = methodSym.getReturnType();
// Could be null for initializer blocks
if (ASTHelpers.isSameType(loggerType, returnType, state)) {
return NO_MATCH;
}
}
// They're using forEnclosingClass inside a method that doesn't produce a logger, or in the
// initializer for some variable that's not a logger. We'll replace this with a reference to a
// class-level logger.
state.incrementCounter(this, parent instanceof VariableTree ? "local-variable" : "inline");
return replaceWithFieldLookup(tree, state);
}
private Description fixModifier(VariableTree field, ClassTree owningClass, VisitorState state) {
ModifiersTree modifiers = field.getModifiers();
Set flags = modifiers.getFlags();
if (flags.containsAll(EXPECTED_MODIFIERS)) {
return NO_MATCH;
}
updateModifierCounters(state, flags);
// We have to add all the modifiers as a single SuggestedFix or they conflict
ImmutableSet.Builder toAdd = ImmutableSet.builder();
SuggestedFix.Builder fix = SuggestedFix.builder();
removeModifiers(field, state, PUBLIC, PROTECTED).ifPresent(fix::merge);
toAdd.add(PRIVATE);
toAdd.add(Modifier.FINAL);
if (flags.contains(FINAL) && canHaveStaticFields(ASTHelpers.getSymbol(owningClass))) {
// We only add static to fields which are already final, or that we're also making final.
// It's a bit dangerous to quietly make something static if it might be getting reassigned.
toAdd.add(STATIC);
}
ImmutableSet newModifiers = toAdd.build();
if (!newModifiers.isEmpty()) {
addModifiers(field, modifiers, state, newModifiers).ifPresent(fix::merge);
}
if (fix.isEmpty()) {
// They're missing some modifiers, but not the ones we've been instructed to change today.
// This is instead of blindly using fix.build(), which would insert a comment if empty.
return NO_MATCH;
}
return describeMatch(field, fix.build());
}
private Description replaceWithFieldLookup(ExpressionTree expr, VisitorState state) {
SuggestedFix.Builder fix = SuggestedFix.builder();
LocalLogger logger = findOrDefineLogger(state, fix);
/*
Sometimes people assign to the logger in, e.g., a static initializer. We don't want to
rewrite this to { logger = logger; }, so we search up the tree to see if we are part
of any assignment to the logger that we're planning to replace this with a reference
to.
*/
if (logger.provenance == LocalLogger.Provenance.ALREADY_PRESENT && logger.sym.isPresent()) {
// There should always be a symbol for ALREADY_PRESENT, but we check just in case.
Symbol target = logger.sym.get();
Tree e = expr;
TreePath path = state.getPath();
do {
if (e instanceof AssignmentTree) {
AssignmentTree assignment = (AssignmentTree) e;
if (ASTHelpers.getSymbol(assignment.getVariable()).equals(target)) {
state.incrementCounter(this, "skip-self-assignment");
return NO_MATCH;
}
}
path = path.getParentPath();
e = path.getLeaf();
} while (e instanceof ExpressionTree);
}
String loggerName = logger.name;
Tree parent = state.getPath().getParentPath().getLeaf();
if (parent instanceof VariableTree
&& ((VariableTree) parent).getName().contentEquals(loggerName)) {
// Instead of making a local shadow of a class member, just use the class member.
return describeMatch(expr, fix.delete(parent).build());
}
if (loggerName.equals(state.getSourceForNode(expr))) {
// Don't rewrite `logger` to `logger`, which runs the formatter over an "unchanged"
// line.
if (fix.isEmpty()) {
// The logger field we want to refer to already exists, and we don't need to
// change this
// line, so there's actually no work to do.
return NO_MATCH;
}
// Produce a fix that inserts the new logger field without changing this line.
return describeMatch(expr, fix.build());
}
return describeMatch(expr, fix.replace(expr, loggerName).build());
}
private void updateModifierCounters(VisitorState state, Set flags) {
// We expect to see all of these, so note when we don't
for (Modifier modifier : ImmutableList.of(STATIC, FINAL)) {
if (!flags.contains(modifier)) {
state.incrementCounter(this, "missing-" + modifier);
}
}
// These we expect to see at most one of, so log whichever is there (or package otherwise)
boolean explicitVisibility = false;
for (Modifier visibility : ImmutableList.of(PUBLIC, Modifier.PRIVATE, PROTECTED)) {
if (flags.contains(visibility)) {
state.incrementCounter(this, "visibility-" + visibility);
explicitVisibility = true;
break;
}
}
if (!explicitVisibility) {
state.incrementCounter(this, "visibility-package");
}
}
private static final class LocalLogger {
LocalLogger(Provenance provenance, Optional sym, String name) {
this.provenance = provenance;
this.sym = sym;
this.name = name;
}
enum Provenance {
ALREADY_PRESENT,
DEFINED_BY_FIX
}
final Provenance provenance;
final Optional sym;
final String name;
}
private LocalLogger findOrDefineLogger(VisitorState state, SuggestedFix.Builder fix) {
return localLogger.computeIfAbsent(
ASTHelpers.getFileName(state.getPath().getCompilationUnit()),
s -> computeLocalLogger(state, fix));
}
private LocalLogger computeLocalLogger(VisitorState state, SuggestedFix.Builder fix) {
Type loggerType = LOGGER_TYPE.get(state);
if (loggerType == null) {
throw new AssertionError("Attempting to define new logger in a file without loggers");
}
ImmutableSet ignoredFields = fieldsToIgnore(state);
ClassTree topLevelClassInFile = outermostClassTree(state.getPath());
ClassSymbol targetClassSym = ASTHelpers.getSymbol(topLevelClassInFile);
for (Tree member : topLevelClassInFile.getMembers()) {
Symbol memberSym = ASTHelpers.getSymbol(member);
if (memberSym instanceof VarSymbol
&& ASTHelpers.isSubtype(memberSym.type, loggerType, state)
&& !ignoredFields.contains(memberSym)) {
// Found some logger defined, let's just use that, unless it needs to be moved.
if (!targetClassSym.isInterface()) {
state.incrementCounter(this, "found-existing");
return new LocalLogger(
LocalLogger.Provenance.ALREADY_PRESENT,
Optional.of(memberSym),
memberSym.getSimpleName().toString());
}
/* This logger belongs to an interface, which means it is public. We'll create a new static
nested class to hold the logger, and make the logger a private member of that class.
*/
fix.delete(member);
return defineNestedClassWithLogger(topLevelClassInFile, state, fix);
}
}
fix.addImport(GOOGLE_LOGGER);
if (targetClassSym.isInterface()) {
// Interfaces should get a nested class, not a normal field.
return defineNestedClassWithLogger(topLevelClassInFile, state, fix);
}
String name =
REASONABLE_LOGGER_NAMES.stream()
.filter(
candidate ->
Iterables.isEmpty(
targetClassSym.members().getSymbolsByName(state.getName(candidate))))
.findFirst()
.orElseThrow(IllegalStateException::new);
String newMember =
String.format(
"private static final FluentLogger %s =" + " FluentLogger.forEnclosingClass();", name);
fix.merge(
SuggestedFixes.addMembers(topLevelClassInFile, state, AdditionPosition.FIRST, newMember));
return new LocalLogger(LocalLogger.Provenance.DEFINED_BY_FIX, Optional.empty(), name);
}
private static LocalLogger defineNestedClassWithLogger(
ClassTree topLevelClassInFile, VisitorState state, SuggestedFix.Builder fix) {
fix.merge(SuggestedFixes.addMembers(topLevelClassInFile, state, NESTED_LOGGER_DEFINITION));
return new LocalLogger(
LocalLogger.Provenance.DEFINED_BY_FIX,
Optional.empty(),
String.format("%s.%s", NESTED_LOGGER_CLASSNAME, NESTED_LOGGER_FIELDNAME));
}
private static ClassTree outermostClassTree(TreePath path) {
ClassTree result = null;
while (path != null) {
Tree leaf = path.getLeaf();
if (leaf instanceof ClassTree) {
result = (ClassTree) leaf;
}
path = path.getParentPath();
}
Verify.verifyNotNull(result, "No enclosing class");
return result;
}
private static boolean canHaveStaticFields(ClassSymbol enclosingClassSym) {
return enclosingClassSym.getNestingKind() == NestingKind.TOP_LEVEL
|| enclosingClassSym.getNestingKind() == NestingKind.MEMBER
&& ((enclosingClassSym.flags() & Flags.STATIC) != 0);
}
@Override
public Description matchIdentifier(IdentifierTree tree, VisitorState state) {
return rehomeLogger(tree, state);
}
@Override
public Description matchMemberSelect(MemberSelectTree tree, VisitorState state) {
return rehomeLogger(tree, state);
}
/**
* If the expression refers to a FluentLogger owned by a class in another file, rewrites it to
* refer to a logger in this file, defining one if necessary.
*/
private Description rehomeLogger(ExpressionTree tree, VisitorState state) {
Symbol sym = ASTHelpers.getSymbol(tree);
if (sym == null) {
return NO_MATCH;
}
Type type = sym.type;
if (!ASTHelpers.isSameType(type, LOGGER_TYPE.get(state), state)) {
return NO_MATCH;
}
Symbol owner = sym.owner;
if (!(owner instanceof ClassSymbol)) {
// This may be looking up FluentLogger itself, as a member of its package, or reading a local.
return NO_MATCH;
}
if (!(isStatic(sym) || tree instanceof IdentifierTree)) {
// We can only be referring to another class's logger statically, or implicitly through a
// superclass as an identifier. This early exit avoids flagging instance field lookups.
return NO_MATCH;
}
/* Loggers owned by public interfaces should be moved regardless of whether they're defined in
the current file, because fields in interfaces must be public, but loggers should be private.
*/
boolean needsMoveFromInterface = owner.isInterface();
Symbol outermostClassOfLogger = findUltimateOwningClass(owner);
ClassTree outermostClassOfFile = null;
for (Tree parent : state.getPath()) {
Symbol ownerSym = ASTHelpers.getSymbol(parent);
if (outermostClassOfLogger.equals(ownerSym)) {
/* Seems to be a logger owned by a class in this file. */
if (!needsMoveFromInterface) {
return NO_MATCH;
}
}
if (parent instanceof ClassTree) {
outermostClassOfFile = (ClassTree) parent;
}
}
if (outermostClassOfFile == null) {
// Impossible, I think?
state.incrementCounter(this, "error-no-outermost-class");
return NO_MATCH;
}
return replaceWithFieldLookup(tree, state);
}
private static Symbol findUltimateOwningClass(Symbol sym) {
Symbol result = sym;
while (sym instanceof ClassSymbol) {
result = sym;
sym = sym.owner;
}
return result;
}
/**
* Fields which we should not use to replace the current expression, because we are in the middle
* of defining them.
*/
private static ImmutableSet fieldsToIgnore(VisitorState state) {
Tree t = state.findEnclosing(VariableTree.class, ClassTree.class);
return t instanceof VariableTree ? ImmutableSet.of(ASTHelpers.getSymbol(t)) : ImmutableSet.of();
}
}
