Add a SpellChecker class with edit distance function.

This will be used later to detect typos and provide suggestions.

--
MOS_MIGRATED_REVID=123761611

1 files changed, 79 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/util/SpellCheckerTest.java b/src/test/java/com/google/devtools/build/lib/util/SpellCheckerTest.java
new file mode 100644
index 0000000000..d0d84e38f6
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/util/SpellCheckerTest.java
@@ -0,0 +1,79 @@
+// 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.util;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link SpellChecker}.
+ */
+@RunWith(JUnit4.class)
+public class SpellCheckerTest {
+
+  private void assertDistance(String s1, String s2, int distance) {
+    assertThat(SpellChecker.editDistance(s1, s2, 100)).isEqualTo(distance);
+    assertThat(SpellChecker.editDistance(s1, s2, distance)).isEqualTo(distance);
+
+    // Symmetry
+    assertThat(SpellChecker.editDistance(s2, s1, 100)).isEqualTo(distance);
+    assertThat(SpellChecker.editDistance(s2, s1, distance)).isEqualTo(distance);
+  }
+
+  @Test
+  public void editDistance_1() throws Exception {
+    // Deletion
+    assertDistance("abcdef", "abdef", 1);
+    assertDistance("abcdef", "abcde", 1);
+    assertDistance("abcdef", "bcdef", 1);
+
+    // Replacement
+    assertDistance("abcdef", "_bcdef", 1);
+    assertDistance("abcdef", "abc_ef", 1);
+    assertDistance("abcdef", "abcde_", 1);
+
+    // Insertion
+    assertDistance("abcdef", "_abcdef", 1);
+    assertDistance("abcdef", "abcd_ef", 1);
+    assertDistance("abcdef", "abcdef_", 1);
+  }
+
+  @Test
+  public void editDistance_general() throws Exception {
+    assertDistance("", "", 0);
+    assertDistance("abcd", "abcd", 0);
+    assertDistance("abcde", "", 5);
+    assertDistance("abcde", "12345", 5);
+    assertDistance("ab", "ba", 2);
+    assertDistance("abba", "acca", 2);
+    assertDistance("abaa", "aaca", 2);
+    assertDistance("kitten", "sitting", 3);
+    assertDistance("kitten kitten", "sitting sitting", 6);
+    assertDistance("flaw", "lawn", 2);
+  }
+
+  @Test
+  public void editDistance_maxDistance() throws Exception {
+    assertThat(SpellChecker.editDistance("kitten", "sitting", 0)).isEqualTo(-1);
+    assertThat(SpellChecker.editDistance("kitten", "sitting", 1)).isEqualTo(-1);
+    assertThat(SpellChecker.editDistance("kitten", "sitting", 2)).isEqualTo(-1);
+    assertThat(SpellChecker.editDistance("kitten", "sitting", 3)).isEqualTo(3);
+    assertThat(SpellChecker.editDistance("kitten", "sitting", 4)).isEqualTo(3);
+
+    assertThat(SpellChecker.editDistance("abcdefg", "s", 2)).isEqualTo(-1);
+  }
+}