Add sections to support string separated by comma

Summary: While working with the StringDiff library, I found that if the data input doesn't contains `\n`, using ::lines() won't provide the desired result. Considering there should be quite some amount of strings built with comma separated way, this should enable more use cases to do the comparison correctly.

Reviewed By: fredemmott

Differential Revision: D26116594

fbshipit-source-id: 77e587e7ca7b10aeff936c0237a157da29664a2e

Author: Brian Hsu

src/StringDiff.php

@@ -16,7 +16,7 @@
 /** Concrete instance of `Diff` for comparing sequences of strings.
  *
  * You can directly pass in vectors of strings to the constructor, or you can
- * use `::lines()` or `::characters()` for convenience in the common cases.
+ * use `::lines()`, `::characters()` or `::commaSeparatedValues()` for convenience in the common cases.
  *
  * @see `getDiff()` to get a `vec<DiffOp<string>>`
  * @see `getUnifiedDiff()` to get a diff suitable for `patch`
@@ -34,6 +34,10 @@ public static function characters(string $a, string $b): this {
     return new self(Str\split($a, ''), Str\split($b, ''));
   }
 
+  public static function commaSeparatedValues(string $a, string $b): this {
+    return new self(Str\split($a, ','), Str\split($b, ','));
+  }
+
   public function getHunks(int $context): vec<vec<DiffOp<string>>> {
     $hunks = vec[];
 

tests/StringDiffTest.php

@@ -48,6 +48,20 @@ public function testDiffCharacters(): void {
     );
   }
 
+  public function testDiffCommaSeparatedValues(): void {
+    $diff = StringDiff::commaSeparatedValues('a,b,c', 'a,b,d')->getDiff();
+    expect(C\count($diff))->toEqual(4);
+
+    expect($diff[0])->toBeInstanceOf(DiffKeepOp::class);
+    expect($diff[1])->toBeInstanceOf(DiffKeepOp::class);
+    expect($diff[2])->toBeInstanceOf(DiffDeleteOp::class);
+    expect($diff[3])->toBeInstanceOf(DiffInsertOp::class);
+
+    expect(Vec\map($diff, $op ==> $op->getContent()))->toEqual(
+      vec['a', 'b', 'c', 'd'],
+    );
+  }
+
   public static function provideExamples(): vec<(string)> {
     return Vec\map(
       /* HH_FIXME[4107] using directly because this is open source */