Create a helper rule for selecting a file from outputs of another rul… (#233)

* Create a helper rule for selecting a file from outputs of another rule or a filegroup by subpath

* Add tests

* Address code review comments

* + formatting

Co-authored-by: c-parsons <cparsons@google.com>

3 files changed, 36 insertions, 0 deletions

diff --git a/tests/select_file/BUILD b/tests/select_file/BUILD
new file mode 100644
index 0000000..e795502
--- /dev/null
+++ b/tests/select_file/BUILD
@@ -0,0 +1,34 @@
+load("//rules:select_file.bzl", "select_file")
+load("//rules:diff_test.bzl", "diff_test")
+
+filegroup(
+    name = "fg",
+    srcs = [
+        "subdir/inner.txt",
+        ":select_me.txt",
+    ],
+)
+
+select_file(
+    name = "select_me",
+    srcs = ":fg",
+    subpath = "select_me.txt",
+)
+
+select_file(
+    name = "select_inner",
+    srcs = ":fg",
+    subpath = "subdir/inner.txt",
+)
+
+diff_test(
+    name = "selected_me",
+    file1 = ":select_me",
+    file2 = ":select_me.txt",
+)
+
+diff_test(
+    name = "selected_inner",
+    file1 = ":select_inner",
+    file2 = "subdir/inner.txt",
+)
diff --git a/tests/select_file/select_me.txt b/tests/select_file/select_me.txt
new file mode 100644
index 0000000..4221a1e
--- /dev/null
+++ b/tests/select_file/select_me.txt
@@ -0,0 +1 @@
+Outer
diff --git a/tests/select_file/subdir/inner.txt b/tests/select_file/subdir/inner.txt
new file mode 100644
index 0000000..d87e45a
--- /dev/null
+++ b/tests/select_file/subdir/inner.txt
@@ -0,0 +1 @@
+Inner