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With inspiration from other libraries
/*
* Copyright (C) 2015 Square, Inc.
*
* 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.squareup.javapoet;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.EnumSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.ListIterator;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Modifier;
import static com.squareup.javapoet.Util.checkArgument;
import static com.squareup.javapoet.Util.checkNotNull;
import static com.squareup.javapoet.Util.checkState;
import static com.squareup.javapoet.Util.join;
import static com.squareup.javapoet.Util.stringLiteralWithDoubleQuotes;
/**
* Converts a {@link JavaFile} to a string suitable to both human- and javac-consumption. This
* honors imports, indentation, and deferred variable names.
*/
final class CodeWriter {
/** Sentinel value that indicates that no user-provided package has been set. */
private static final String NO_PACKAGE = new String();
private final String indent;
private final LineWrapper out;
private int indentLevel;
private boolean javadoc = false;
private boolean comment = false;
private String packageName = NO_PACKAGE;
private final List typeSpecStack = new ArrayList<>();
private final Set staticImportClassNames;
private final Set staticImports;
private final Map importedTypes;
private final Map importableTypes = new LinkedHashMap<>();
private final Set referencedNames = new LinkedHashSet<>();
private boolean trailingNewline;
/**
* When emitting a statement, this is the line of the statement currently being written. The first
* line of a statement is indented normally and subsequent wrapped lines are double-indented. This
* is -1 when the currently-written line isn't part of a statement.
*/
int statementLine = -1;
CodeWriter(Appendable out) {
this(out, " ", Collections.emptySet());
}
CodeWriter(Appendable out, String indent, Set staticImports) {
this(out, indent, Collections.emptyMap(), staticImports);
}
CodeWriter(Appendable out, String indent, Map importedTypes,
Set staticImports) {
this.out = new LineWrapper(out, indent, 100);
this.indent = checkNotNull(indent, "indent == null");
this.importedTypes = checkNotNull(importedTypes, "importedTypes == null");
this.staticImports = checkNotNull(staticImports, "staticImports == null");
this.staticImportClassNames = new LinkedHashSet<>();
for (String signature : staticImports) {
staticImportClassNames.add(signature.substring(0, signature.lastIndexOf('.')));
}
}
public Map importedTypes() {
return importedTypes;
}
public CodeWriter indent() {
return indent(1);
}
public CodeWriter indent(int levels) {
indentLevel += levels;
return this;
}
public CodeWriter unindent() {
return unindent(1);
}
public CodeWriter unindent(int levels) {
checkArgument(indentLevel - levels >= 0, "cannot unindent %s from %s", levels, indentLevel);
indentLevel -= levels;
return this;
}
public CodeWriter pushPackage(String packageName) {
checkState(this.packageName == NO_PACKAGE, "package already set: %s", this.packageName);
this.packageName = checkNotNull(packageName, "packageName == null");
return this;
}
public CodeWriter popPackage() {
checkState(this.packageName != NO_PACKAGE, "package already set: %s", this.packageName);
this.packageName = NO_PACKAGE;
return this;
}
public CodeWriter pushType(TypeSpec type) {
this.typeSpecStack.add(type);
return this;
}
public CodeWriter popType() {
this.typeSpecStack.remove(typeSpecStack.size() - 1);
return this;
}
public void emitComment(CodeBlock codeBlock) throws IOException {
trailingNewline = true; // Force the '//' prefix for the comment.
comment = true;
try {
emit(codeBlock);
emit("\n");
} finally {
comment = false;
}
}
public void emitJavadoc(CodeBlock javadocCodeBlock) throws IOException {
if (javadocCodeBlock.isEmpty()) return;
emit("/**\n");
javadoc = true;
try {
emit(javadocCodeBlock);
} finally {
javadoc = false;
}
emit(" */\n");
}
public void emitAnnotations(List annotations, boolean inline) throws IOException {
for (AnnotationSpec annotationSpec : annotations) {
annotationSpec.emit(this, inline);
emit(inline ? " " : "\n");
}
}
/**
* Emits {@code modifiers} in the standard order. Modifiers in {@code implicitModifiers} will not
* be emitted.
*/
public void emitModifiers(Set modifiers, Set implicitModifiers)
throws IOException {
if (modifiers.isEmpty()) return;
for (Modifier modifier : EnumSet.copyOf(modifiers)) {
if (implicitModifiers.contains(modifier)) continue;
emitAndIndent(modifier.name().toLowerCase(Locale.US));
emitAndIndent(" ");
}
}
public void emitModifiers(Set modifiers) throws IOException {
emitModifiers(modifiers, Collections.emptySet());
}
/**
* Emit type variables with their bounds. This should only be used when declaring type variables;
* everywhere else bounds are omitted.
*/
public void emitTypeVariables(List typeVariables) throws IOException {
if (typeVariables.isEmpty()) return;
emit("<");
boolean firstTypeVariable = true;
for (TypeVariableName typeVariable : typeVariables) {
if (!firstTypeVariable) emit(", ");
emitAnnotations(typeVariable.annotations, true);
emit("$L", typeVariable.name);
boolean firstBound = true;
for (TypeName bound : typeVariable.bounds) {
emit(firstBound ? " extends $T" : " & $T", bound);
firstBound = false;
}
firstTypeVariable = false;
}
emit(">");
}
public CodeWriter emit(String s) throws IOException {
return emitAndIndent(s);
}
public CodeWriter emit(String format, Object... args) throws IOException {
return emit(CodeBlock.of(format, args));
}
public CodeWriter emit(CodeBlock codeBlock) throws IOException {
int a = 0;
ClassName deferredTypeName = null; // used by "import static" logic
ListIterator partIterator = codeBlock.formatParts.listIterator();
while (partIterator.hasNext()) {
String part = partIterator.next();
switch (part) {
case "$L":
emitLiteral(codeBlock.args.get(a++));
break;
case "$N":
emitAndIndent((String) codeBlock.args.get(a++));
break;
case "$S":
String string = (String) codeBlock.args.get(a++);
// Emit null as a literal null: no quotes.
emitAndIndent(string != null
? stringLiteralWithDoubleQuotes(string, indent)
: "null");
break;
case "$T":
TypeName typeName = (TypeName) codeBlock.args.get(a++);
if (typeName.isAnnotated()) {
typeName.emitAnnotations(this);
typeName = typeName.withoutAnnotations();
}
// defer "typeName.emit(this)" if next format part will be handled by the default case
if (typeName instanceof ClassName && partIterator.hasNext()) {
if (!codeBlock.formatParts.get(partIterator.nextIndex()).startsWith("$")) {
ClassName candidate = (ClassName) typeName;
if (staticImportClassNames.contains(candidate.canonicalName)) {
checkState(deferredTypeName == null, "pending type for static import?!");
deferredTypeName = candidate;
break;
}
}
}
typeName.emit(this);
break;
case "$$":
emitAndIndent("$");
break;
case "$>":
indent();
break;
case "$<":
unindent();
break;
case "$[":
checkState(statementLine == -1, "statement enter $[ followed by statement enter $[");
statementLine = 0;
break;
case "$]":
checkState(statementLine != -1, "statement exit $] has no matching statement enter $[");
if (statementLine > 0) {
unindent(2); // End a multi-line statement. Decrease the indentation level.
}
statementLine = -1;
break;
case "$W":
out.wrappingSpace(indentLevel + 2);
break;
case "$Z":
out.zeroWidthSpace(indentLevel + 2);
break;
default:
// handle deferred type
if (deferredTypeName != null) {
if (part.startsWith(".")) {
if (emitStaticImportMember(deferredTypeName.canonicalName, part)) {
// okay, static import hit and all was emitted, so clean-up and jump to next part
deferredTypeName = null;
break;
}
}
deferredTypeName.emit(this);
deferredTypeName = null;
}
emitAndIndent(part);
break;
}
}
return this;
}
public CodeWriter emitWrappingSpace() throws IOException {
out.wrappingSpace(indentLevel + 2);
return this;
}
private static String extractMemberName(String part) {
checkArgument(Character.isJavaIdentifierStart(part.charAt(0)), "not an identifier: %s", part);
for (int i = 1; i <= part.length(); i++) {
if (!SourceVersion.isIdentifier(part.substring(0, i))) {
return part.substring(0, i - 1);
}
}
return part;
}
private boolean emitStaticImportMember(String canonical, String part) throws IOException {
String partWithoutLeadingDot = part.substring(1);
if (partWithoutLeadingDot.isEmpty()) return false;
char first = partWithoutLeadingDot.charAt(0);
if (!Character.isJavaIdentifierStart(first)) return false;
String explicit = canonical + "." + extractMemberName(partWithoutLeadingDot);
String wildcard = canonical + ".*";
if (staticImports.contains(explicit) || staticImports.contains(wildcard)) {
emitAndIndent(partWithoutLeadingDot);
return true;
}
return false;
}
private void emitLiteral(Object o) throws IOException {
if (o instanceof TypeSpec) {
TypeSpec typeSpec = (TypeSpec) o;
typeSpec.emit(this, null, Collections.emptySet());
} else if (o instanceof AnnotationSpec) {
AnnotationSpec annotationSpec = (AnnotationSpec) o;
annotationSpec.emit(this, true);
} else if (o instanceof CodeBlock) {
CodeBlock codeBlock = (CodeBlock) o;
emit(codeBlock);
} else {
emitAndIndent(String.valueOf(o));
}
}
/**
* Returns the best name to identify {@code className} with in the current context. This uses the
* available imports and the current scope to find the shortest name available. It does not honor
* names visible due to inheritance.
*/
String lookupName(ClassName className) {
// Find the shortest suffix of className that resolves to className. This uses both local type
// names (so `Entry` in `Map` refers to `Map.Entry`). Also uses imports.
boolean nameResolved = false;
for (ClassName c = className; c != null; c = c.enclosingClassName()) {
ClassName resolved = resolve(c.simpleName());
nameResolved = resolved != null;
if (resolved != null && Objects.equals(resolved.canonicalName, c.canonicalName)) {
int suffixOffset = c.simpleNames().size() - 1;
return join(".", className.simpleNames().subList(
suffixOffset, className.simpleNames().size()));
}
}
// If the name resolved but wasn't a match, we're stuck with the fully qualified name.
if (nameResolved) {
return className.canonicalName;
}
// If the class is in the same package, we're done.
if (Objects.equals(packageName, className.packageName())) {
referencedNames.add(className.topLevelClassName().simpleName());
return join(".", className.simpleNames());
}
// We'll have to use the fully-qualified name. Mark the type as importable for a future pass.
if (!javadoc) {
importableType(className);
}
return className.canonicalName;
}
private void importableType(ClassName className) {
if (className.packageName().isEmpty()) {
return;
}
ClassName topLevelClassName = className.topLevelClassName();
String simpleName = topLevelClassName.simpleName();
ClassName replaced = importableTypes.put(simpleName, topLevelClassName);
if (replaced != null) {
importableTypes.put(simpleName, replaced); // On collision, prefer the first inserted.
}
}
/**
* Returns the class referenced by {@code simpleName}, using the current nesting context and
* imports.
*/
// TODO(jwilson): also honor superclass members when resolving names.
private ClassName resolve(String simpleName) {
// Match a child of the current (potentially nested) class.
for (int i = typeSpecStack.size() - 1; i >= 0; i--) {
TypeSpec typeSpec = typeSpecStack.get(i);
for (TypeSpec visibleChild : typeSpec.typeSpecs) {
if (Objects.equals(visibleChild.name, simpleName)) {
return stackClassName(i, simpleName);
}
}
}
// Match the top-level class.
if (typeSpecStack.size() > 0 && Objects.equals(typeSpecStack.get(0).name, simpleName)) {
return ClassName.get(packageName, simpleName);
}
// Match an imported type.
ClassName importedType = importedTypes.get(simpleName);
if (importedType != null) return importedType;
// No match.
return null;
}
/** Returns the class named {@code simpleName} when nested in the class at {@code stackDepth}. */
private ClassName stackClassName(int stackDepth, String simpleName) {
ClassName className = ClassName.get(packageName, typeSpecStack.get(0).name);
for (int i = 1; i <= stackDepth; i++) {
className = className.nestedClass(typeSpecStack.get(i).name);
}
return className.nestedClass(simpleName);
}
/**
* Emits {@code s} with indentation as required. It's important that all code that writes to
* {@link #out} does it through here, since we emit indentation lazily in order to avoid
* unnecessary trailing whitespace.
*/
CodeWriter emitAndIndent(String s) throws IOException {
boolean first = true;
for (String line : s.split("\n", -1)) {
// Emit a newline character. Make sure blank lines in Javadoc & comments look good.
if (!first) {
if ((javadoc || comment) && trailingNewline) {
emitIndentation();
out.append(javadoc ? " *" : "//");
}
out.append("\n");
trailingNewline = true;
if (statementLine != -1) {
if (statementLine == 0) {
indent(2); // Begin multiple-line statement. Increase the indentation level.
}
statementLine++;
}
}
first = false;
if (line.isEmpty()) continue; // Don't indent empty lines.
// Emit indentation and comment prefix if necessary.
if (trailingNewline) {
emitIndentation();
if (javadoc) {
out.append(" * ");
} else if (comment) {
out.append("// ");
}
}
out.append(line);
trailingNewline = false;
}
return this;
}
private void emitIndentation() throws IOException {
for (int j = 0; j < indentLevel; j++) {
out.append(indent);
}
}
/**
* Returns the types that should have been imported for this code. If there were any simple name
* collisions, that type's first use is imported.
*/
Map suggestedImports() {
Map result = new LinkedHashMap<>(importableTypes);
result.keySet().removeAll(referencedNames);
return result;
}
}