fix: permit more label syntax when pre-computing outputs

examples/path_mappings/BUILD.bazel

@@ -9,7 +9,9 @@ load("@bazel_skylib//rules:build_test.bzl", "build_test")
 # bazel-bin/examples/path_mappings/foo.d.ts
 ts_project(
     name = "path_mappings",
-    srcs = ["foo.ts"],
+    # Use a fully-qualified label as a test that the macro logic still produces
+    # the expected pre-declared output file for foo.js
+    srcs = ["//examples/path_mappings:foo.ts"],
     declaration = True,
     validate = False,
     deps = [
@@ -20,5 +22,5 @@ ts_project(
 
 build_test(
     name = "path_mappings_test",
-    targets = [":path_mappings"],
+    targets = [":foo.js"],
 )

examples/srcs/BUILD.bazel

@@ -40,9 +40,11 @@ write_file(
 ts_project(
     name = "srcs-generated",
     # Demonstrates that you can mix sources with generated files
+    # (Also verifies that relative labels work with macro logic for predeclared outputs)
     srcs = [
-        "a.ts",
-        "generated.ts",
+        "//examples/srcs:a.ts",
+        ":b.ts",
+        ":generated.ts",
     ],
     out_dir = "generated",
 )

ts/private/ts_lib.bzl

@@ -201,6 +201,9 @@ def _replace_ext(f, ext_map):
     return None
 
 def _to_out_path(f, out_dir, root_dir):
+    # convert to a label first, to normalize syntax like
+    # srcs = ["@//path/to:a.ts", "//path/to:b.ts", ":c.ts", "d.ts"]
+    f = f[f.find(":") + 1:]
     if root_dir:
         f = f.removeprefix(root_dir + "/")
     if out_dir: