From 23ba4a8416e3de077ff85cf59b95ccefe8ef3892 Mon Sep 17 00:00:00 2001
From: Vladimir Moskva <vladmos@google.com>
Date: Tue, 21 Feb 2017 15:30:54 +0000
Subject: Augmented assignments don't evaluate lhs multiple times

--
PiperOrigin-RevId: 148092963
MOS_MIGRATED_REVID=148092963
---
 .../build/lib/syntax/SkylarkEvaluationTest.java    | 43 ++++++++++++++++++++++
 1 file changed, 43 insertions(+)

(limited to 'src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java')

diff --git a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
index 0a701e0e5c..6353c1270e 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
@@ -908,6 +908,49 @@ public class SkylarkEvaluationTest extends EvaluationTest {
         "foo = f1(41)").testLookup("foo", 42);
   }
 
+  @Test
+  public void testAugmentedAssignmentHasNoSideEffects() throws Exception {
+    new SkylarkTest().setUp(
+        "counter = [0]",
+        "value = [1, 2]",
+        "",
+        "def f():",
+        "  counter[0] = counter[0] + 1",
+        "  return value",
+        "",
+        "f()[1] += 1")  // `f()` should be called only once here
+        .testLookup("counter", MutableList.of(env, 1));
+  }
+
+  @Test
+  public void testAugmentedAssignmentNotAllowedForListLiterals() throws Exception {
+    new SkylarkTest().testIfErrorContains("Cannot perform augment assignment on a list literal",
+        "def f(a, b):",
+        "  [a, b] += []",
+        "f(1, 2)");
+  }
+
+  @Test
+  public void testAssignmentEvaluationOrder() throws Exception {
+    new SkylarkTest().setUp(
+        "ordinary = []",
+        "augmented = []",
+        "value = [1, 2]",
+        "",
+        "def f(record):",
+        "  record.append('f')",
+        "  return value",
+        "",
+        "def g(record):",
+        "  record.append('g')",
+        "  return value",
+        "",
+        "f(ordinary)[0] = g(ordinary)[1]",
+        "f(augmented)[0] += g(augmented)[1]")
+        .testLookup("ordinary", MutableList.of(env, "g", "f"))    // This order is consistent
+        .testLookup("augmented", MutableList.of(env, "f", "g"));  // with Python
+  }
+
   @Test
   public void testStaticDirectJavaCall() throws Exception {
     new SkylarkTest().update("Mock", Mock.class).setUp("val = Mock.value_of('8')")
-- 
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