@StarlarkMethod.trustReturnsValid

Summary:
When returning from native functions, Starlark by default checks that returned value is a valid Starlark object (i. e. `String`, `Boolean` or implements `StarlarkValue`). That check is relatively expensive for cheap calls like `dict.get`.

`StarlarkMethod.trustReturnsValid` when used with native function disables this check.

This diff will likely not produce noticeable speedup, but the check is visible in profiler.

Upstream PR: bazelbuild/bazel#13012

Reviewed By: mzlee

fbshipit-source-id: 29e146503a0653a5629dc526c76d64e6f5e5b2f7

third-party/java/bazel/README.facebook

@@ -16,3 +16,4 @@ exists here to simplify sync with upstream if we ever do it.
 * D26877128 Faster parameter type check for Object
 * D26877129 Faster dict.keys
 * D26877121 Intern identifiers
+* D26877118 @StarlarkMethod.trustReturnsValid

third-party/java/bazel/src/main/java/net/starlark/java/annot/StarlarkMethod.java

@@ -165,6 +165,11 @@
    */
   boolean allowReturnNones() default false;
 
+  /**
+   * When true, Starlark interpreter does not validate function returns a valid Starlark runtime object.
+   */
+  boolean trustReturnsValid() default false;
+
   /**
    * If true, the StarlarkThread will be passed as an argument of the annotated function. (Thus, the
    * annotated method signature must contain StarlarkThread as a parameter. See the interface-level

third-party/java/bazel/src/main/java/net/starlark/java/eval/Dict.java

@@ -180,6 +180,7 @@ public Iterator<K> iterator() {
             named = true,
             doc = "The default value to use (instead of None) if the key is not found.")
       },
+      trustReturnsValid = true,
       useStarlarkThread = true)
   // TODO(adonovan): This method is named get2 as a temporary workaround for a bug in
   // StarlarkAnnotations.getStarlarkMethod. The two 'get' methods cause it to get
@@ -213,6 +214,7 @@ public Object get2(Object key, Object defaultValue, StarlarkThread thread) throw
             named = true,
             doc = "a default value if the key is absent."),
       },
+      trustReturnsValid = true,
       useStarlarkThread = true)
   public Object pop(Object key, Object defaultValue, StarlarkThread thread) throws EvalException {
     Starlark.checkMutable(this);
@@ -264,7 +266,8 @@ public Tuple popitem() throws EvalException {
             defaultValue = "None",
             named = true,
             doc = "a default value if the key is absent."),
-      })
+      },
+      trustReturnsValid = true)
   public V setdefault(K key, V defaultValue) throws EvalException {
     Starlark.checkMutable(this);
     Starlark.checkHashable(key);

third-party/java/bazel/src/main/java/net/starlark/java/eval/MethodDescriptor.java

@@ -70,6 +70,7 @@ private MethodDescriptor(
       boolean extraKeywords,
       boolean selfCall,
       boolean allowReturnNones,
+      boolean trustReturnsValid,
       boolean useStarlarkThread,
       boolean useStarlarkSemantics) {
     this.method = method;
@@ -94,7 +95,8 @@ private MethodDescriptor(
       howToHandleReturn = HowToHandleReturn.NULL_TO_NONE;
     } else if (StarlarkValue.class.isAssignableFrom(ret)
         || String.class == ret
-        || Boolean.class == ret) {
+        || Boolean.class == ret
+        || trustReturnsValid) {
       howToHandleReturn =
           allowReturnNones ? HowToHandleReturn.NULL_TO_NONE : HowToHandleReturn.ERROR_ON_NULL;
     } else if (ret == int.class) {
@@ -145,6 +147,7 @@ static MethodDescriptor of(
         !annotation.extraKeywords().name().isEmpty(),
         annotation.selfCall(),
         annotation.allowReturnNones(),
+        annotation.trustReturnsValid(),
         annotation.useStarlarkThread(),
         annotation.useStarlarkSemantics());
   }

third-party/java/bazel/src/main/java/net/starlark/java/eval/MethodLibrary.java

@@ -40,7 +40,8 @@ class MethodLibrary {
               + "or if no arguments are given. "
               + "<pre class=\"language-python\">min(2, 5, 4) == 2\n"
               + "min([5, 6, 3]) == 3</pre>",
-      extraPositionals = @Param(name = "args", doc = "The elements to be checked."))
+      extraPositionals = @Param(name = "args", doc = "The elements to be checked."),
+      trustReturnsValid = true)
   public Object min(Sequence<?> args) throws EvalException {
     return findExtreme(args, Starlark.ORDERING.reverse());
   }
@@ -54,7 +55,8 @@ public Object min(Sequence<?> args) throws EvalException {
               + "or if no arguments are given. "
               + "<pre class=\"language-python\">max(2, 5, 4) == 5\n"
               + "max([5, 6, 3]) == 6</pre>",
-      extraPositionals = @Param(name = "args", doc = "The elements to be checked."))
+      extraPositionals = @Param(name = "args", doc = "The elements to be checked."),
+      trustReturnsValid = true)
   public Object max(Sequence<?> args) throws EvalException {
     return findExtreme(args, Starlark.ORDERING);
   }
@@ -625,6 +627,7 @@ public boolean hasattr(Object obj, String name, StarlarkThread thread) throws Ev
                 "The default value to return in case the struct "
                     + "doesn't have an attribute of the given name.")
       },
+      trustReturnsValid = true,
       useStarlarkThread = true)
   public Object getattr(Object obj, String name, Object defaultValue, StarlarkThread thread)
       throws EvalException, InterruptedException {

third-party/java/bazel/src/main/java/net/starlark/java/eval/StarlarkList.java

@@ -535,7 +535,8 @@ public int index(Object x, Object start, Object end) throws EvalException {
             },
             defaultValue = "-1",
             doc = "The index of the item.")
-      })
+      },
+      trustReturnsValid = true)
   public Object pop(Object i) throws EvalException {
     int arg = i == Starlark.NONE ? -1 : Starlark.toInt(i, "i");
     int index = EvalUtils.getSequenceIndex(arg, size);