// Copyright 2016 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.syntax;
import com.google.devtools.build.lib.events.Location;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModule;
import com.google.devtools.build.lib.skylarkinterface.SkylarkModuleCategory;
import com.google.devtools.build.lib.syntax.SkylarkMutable.MutableMap;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.annotation.Nullable;
/**
* Skylark Dict module.
*/
@SkylarkModule(name = "dict",
category = SkylarkModuleCategory.BUILTIN,
doc = "A language built-in type representating a dictionary (associative mapping). "
+ "Dictionaries may be constructed with a special literal syntax:<br>"
+ "<pre class=\"language-python\">d = {\"a\": 2, \"b\": 5}</pre>"
+ "Use square brackets to access elements:<br>"
+ "<pre class=\"language-python\">e = d[\"a\"] # e == 2</pre>"
+ "Like lists, they can also be constructed using a comprehension syntax:<br>"
+ "<pre class=\"language-python\">d = {i: 2*i for i in range(20)}\n"
+ "e = d[8] # e == 16</pre>"
+ "See also the <a href=\"globals.html#dict\">dict()</a> constructor function. "
+ "<p>Iterating over a dict is equivalent to iterating over its keys. The <code>in</code> "
+ "operator tests for membership in the keyset of the dict.<br>"
+ "<pre class=\"language-python\">\"a\" in {\"a\" : 2, \"b\" : 5} # evaluates as True</pre>"
+ "The iteration order for a dict is deterministic but not specified. When constructing a dict "
+ "using any of the above methods, if there are two identical keys with conflicting values "
+ "then the last value takes precedence."
)
public final class SkylarkDict<K, V>
extends MutableMap<K, V> implements Map<K, V>, SkylarkIndexable {
private final LinkedHashMap<K, V> contents = new LinkedHashMap<>();
private final Mutability mutability;
@Override
public Mutability mutability() {
return mutability;
}
private SkylarkDict(@Nullable Environment env) {
mutability = env == null ? Mutability.IMMUTABLE : env.mutability();
}
/** @return a dict mutable in given environment only */
public static <K, V> SkylarkDict<K, V> of(@Nullable Environment env) {
return new SkylarkDict<>(env);
}
/** @return a dict mutable in given environment only, with given initial key and value */
public static <K, V> SkylarkDict<K, V> of(@Nullable Environment env, K k, V v) {
return SkylarkDict.<K, V>of(env).putUnsafe(k, v);
}
/** @return a dict mutable in given environment only, with two given initial key value pairs */
public static <K, V> SkylarkDict<K, V> of(
@Nullable Environment env, K k1, V v1, K k2, V v2) {
return SkylarkDict.<K, V>of(env).putUnsafe(k1, v1).putUnsafe(k2, v2);
}
/** @return a dict mutable in given environment only, with contents copied from given map */
public static <K, V> SkylarkDict<K, V> copyOf(
@Nullable Environment env, Map<? extends K, ? extends V> m) {
return SkylarkDict.<K, V>of(env).putAllUnsafe(m);
}
private SkylarkDict<K, V> putUnsafe(K k, V v) {
contents.put(k, v);
return this;
}
private <KK extends K, VV extends V> SkylarkDict putAllUnsafe(Map<KK, VV> m) {
for (Map.Entry<KK, VV> e : m.entrySet()) {
contents.put(e.getKey(), e.getValue());
}
return this;
}
/**
* @return The underlying contents is a (usually) mutable data structure.
* Read access is forwarded to these contents.
* This object must not be modified outside an {@link Environment}
* with a correct matching {@link Mutability},
* which should be checked beforehand using {@link #checkMutable}.
* it need not be an instance of {@link com.google.common.collect.ImmutableMap}.
*/
@Override
protected Map<K, V> getContentsUnsafe() {
return contents;
}
/**
* Put an entry into a SkylarkDict.
* @param k the key
* @param v the associated value
* @param loc a {@link Location} in case of error
* @param env an {@link Environment}, to check Mutability
* @throws EvalException if the key is invalid
*/
public void put(K k, V v, Location loc, Environment env) throws EvalException {
checkMutable(loc, env);
EvalUtils.checkValidDictKey(k);
contents.put(k, v);
}
/**
* Put all the entries from a given dict into the SkylarkDict.
* @param m the map to copy
* @param loc a {@link Location} in case of error
* @param env an {@link Environment}, to check Mutability
* @throws EvalException if some key is invalid
*/
public <KK extends K, VV extends V> void putAll(Map<KK, VV> m, Location loc, Environment env)
throws EvalException {
checkMutable(loc, env);
for (Map.Entry<KK, VV> e : m.entrySet()) {
KK k = e.getKey();
EvalUtils.checkValidDictKey(k);
contents.put(k, e.getValue());
}
}
/** @return the first key in the dict */
K firstKey() {
return contents.entrySet().iterator().next().getKey();
}
/**
* Delete the entry associated to a key.
* @param key the key to delete
* @param loc a {@link Location} in case of error
* @param env an {@link Environment}, to check Mutability
* @return the value associated to the key, or {@code null} if not present
* @throws EvalException if the dict is frozen.
*/
V remove(Object key, Location loc, Environment env) throws EvalException {
checkMutable(loc, env);
return contents.remove(key);
}
/**
* Clear the dict.
* @param loc a {@link Location} in case of error
* @param env an {@link Environment}, to check Mutability
* @throws EvalException if the dict is frozen.
*/
void clear(Location loc, Environment env) throws EvalException {
checkMutable(loc, env);
contents.clear();
}
// Other methods
@Override
public void write(Appendable buffer, char quotationMark) {
Printer.printList(buffer, entrySet(), "{", ", ", "}", null, quotationMark);
}
/**
* Cast a SkylarkDict to a {@code Map<K, V>} after checking its current contents.
* Treat None as meaning the empty ImmutableMap.
* @param obj the Object to cast. null and None are treated as an empty list.
* @param keyType the expected class of keys
* @param valueType the expected class of values
* @param description a description of the argument being converted, or null, for debugging
*/
public static <K, V> SkylarkDict<K, V> castSkylarkDictOrNoneToDict(
Object obj, Class<K> keyType, Class<V> valueType, @Nullable String description)
throws EvalException {
if (EvalUtils.isNullOrNone(obj)) {
return empty();
}
if (obj instanceof SkylarkDict) {
return ((SkylarkDict<?, ?>) obj).getContents(keyType, valueType, description);
}
throw new EvalException(
null,
Printer.format(
"%s is not of expected type dict or NoneType",
description == null ? Printer.repr(obj) : String.format("'%s'", description)));
}
/**
* Cast a SkylarkDict to a {@code SkylarkDict<K, V>} after checking its current contents.
* @param keyType the expected class of keys
* @param valueType the expected class of values
* @param description a description of the argument being converted, or null, for debugging
*/
@SuppressWarnings("unchecked")
public <KeyType, ValueType> SkylarkDict<KeyType, ValueType> getContents(
Class<KeyType> keyType, Class<ValueType> valueType, @Nullable String description)
throws EvalException {
Object keyDescription = description == null
? null : Printer.formattable("'%s' key", description);
Object valueDescription = description == null
? null : Printer.formattable("'%s' value", description);
for (Map.Entry<?, ?> e : this.entrySet()) {
SkylarkType.checkType(e.getKey(), keyType, keyDescription);
SkylarkType.checkType(e.getValue(), valueType, valueDescription);
}
return (SkylarkDict<KeyType, ValueType>) this;
}
@Override
public final Object getIndex(Object key, Location loc) throws EvalException {
if (!this.containsKey(key)) {
throw new EvalException(loc, Printer.format("key %r not found in dictionary", key));
}
return this.get(key);
}
@Override
public final boolean containsKey(Object key, Location loc) throws EvalException {
return this.containsKey(key);
}
public static <K, V> SkylarkDict<K, V> plus(
SkylarkDict<? extends K, ? extends V> left,
SkylarkDict<? extends K, ? extends V> right,
@Nullable Environment env) {
SkylarkDict<K, V> result = SkylarkDict.<K, V>of(env);
result.putAllUnsafe(left);
result.putAllUnsafe(right);
return result;
}
private static final SkylarkDict<?, ?> EMPTY = of(null);
public static <K, V> SkylarkDict<K, V> empty() {
return (SkylarkDict<K, V>) EMPTY;
}
}