write_file: support different line endings (#150)

The user can specify which line endings they want
write_file to use. This helps avoiding line ending
mismatches with diff_test.

Example: diff_test verifies that a rule generates
correct output by comparing it to a checked-in
"golden" file. Both files are text files, and the
user builds on Windows but the golden file was
written on Linux and git checkout preserved
original line endings.

Without explicitly specifying which line endings
to use, this diff_test would fail on an otherwise
good output.

With explicit line endings we don't need to check
in the golden file to git, we can just generate it
with "auto" line endings.

1 files changed, 47 insertions, 0 deletions

diff --git a/tests/write_file/BUILD b/tests/write_file/BUILD
index 321bcc0..9ea3609 100644
--- a/tests/write_file/BUILD
+++ b/tests/write_file/BUILD
@@ -32,6 +32,7 @@
 #   field of it, so we assert that that field contains the output file of the
 #   rule
 
+load("//rules:diff_test.bzl", "diff_test")
 load("//rules:write_file.bzl", "write_file")
 
 licenses(["notice"])
@@ -117,3 +118,49 @@ write_file(
     ],
     is_executable = True,
 )
+
+write_file(
+    name = "newline_unix_actual",
+    out = "out/newline_unix_actual.txt",
+    content = [
+        "ab",
+        "cd",
+        "ef",
+    ],
+    newline = "unix",
+)
+
+write_file(
+    name = "newline_unix_exp",
+    out = "out/newline_unix_exp.txt",
+    content = ["ab\ncd\nef"],
+)
+
+diff_test(
+    name = "unix_line_ending_test",
+    file1 = ":newline_unix_actual",
+    file2 = ":newline_unix_exp",
+)
+
+write_file(
+    name = "newline_win_actual",
+    out = "out/newline_win_actual.txt",
+    content = [
+        "ab",
+        "cd",
+        "ef",
+    ],
+    newline = "windows",
+)
+
+write_file(
+    name = "newline_win_exp",
+    out = "out/newline_win_exp.txt",
+    content = ["ab\r\ncd\r\nef"],
+)
+
+diff_test(
+    name = "win_line_ending_test",
+    file1 = ":newline_win_actual",
+    file2 = ":newline_win_exp",
+)