More concise, diff-compatible header when changing the first line

fredemmott · fredemmott · commit 99d4ff397d0d · 2018-09-21T13:51:26.000-07:00
diff --git a/src/StringDiff.php b/src/StringDiff.php
@@ -130,12 +130,14 @@ private function getUnifiedDiffHunk(
     invariant($old_start !== null, 'failed to find an old pos');
     invariant($new_start !== null, 'failed to find a new pos');
 
+    $format = ($start, $lines) ==> ($start === 1 && $lines === 1)
+      ? '1'
+      : Str\format('%d,%d', $start, $lines);
+
     return Str\format(
-      "@@ -%d,%d +%d,%d @@\n",
-      $old_start + 1,
-      $old_lines,
-      $new_start + 1,
-      $new_lines,
+      "@@ -%s +%s @@\n",
+      $format($old_start + 1, $old_lines),
+      $format($new_start + 1, $new_lines),
     ).Str\join($lines, "\n")."\n";
   }
 }
diff --git a/tests/examples/one_line_to_two.a b/tests/examples/one_line_to_two.a
@@ -0,0 +1 @@
+Foo
diff --git a/tests/examples/one_line_to_two.b b/tests/examples/one_line_to_two.b
@@ -0,0 +1,2 @@
+Bar
+Baz
diff --git a/tests/examples/one_line_to_two.udiff.expect b/tests/examples/one_line_to_two.udiff.expect
@@ -0,0 +1,4 @@
+@@ -1 +1,2 @@
+-Foo
++Bar
++Baz
diff --git a/tests/examples/replace_word.a b/tests/examples/replace_word.a
@@ -0,0 +1 @@
+Framework
diff --git a/tests/examples/replace_word.b b/tests/examples/replace_word.b
@@ -0,0 +1 @@
+Facebook
diff --git a/tests/examples/replace_word.udiff.expect b/tests/examples/replace_word.udiff.expect
@@ -0,0 +1,3 @@
+@@ -1 +1 @@
+-Framework
++Facebook
diff --git a/tests/examples/two_lines_to_one.a b/tests/examples/two_lines_to_one.a
@@ -0,0 +1,2 @@
+Foo
+Bar
diff --git a/tests/examples/two_lines_to_one.b b/tests/examples/two_lines_to_one.b
@@ -0,0 +1 @@
+Baz
diff --git a/tests/examples/two_lines_to_one.udiff.expect b/tests/examples/two_lines_to_one.udiff.expect
@@ -0,0 +1,4 @@
+@@ -1,2 +1 @@
+-Foo
+-Bar
++Baz

-Original file line number
+Diff line change
@@ @@ -0,0 +1,4 @@ @@
 +@@ -1 +1,2 @@
 +-Foo
 ++Bar
 ++Baz
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+@@ -1 +1 @@`
	`2`	`+-Framework`
	`3`	`++Facebook`