feat: add a new source_root attribute

examples/source_root/BUILD.bazel

@@ -0,0 +1,39 @@
+load("@aspect_bazel_lib//lib:write_source_files.bzl", "write_source_files")
+load("@aspect_rules_swc//swc:defs.bzl", "swc")
+
+# Specifies a custom location where a debugger should locate source files instead of relative source 
+# locations. This string is treated verbatim inside the source-map where you can use a path or a URL.
+swc(
+    name = "compile",
+    srcs = ["in.ts"],
+    source_maps = True,
+    # The custom location can an URL
+    source_root = "https://my-website.com/debug/source/",
+)
+
+swc(
+    name = "compile_subdir",
+    srcs = ["src/subdir.ts"],
+    root_dir = "src",
+    source_maps = True,
+    # The custom location can be a path
+    source_root = "../../../debug/source",
+)
+
+# Assert that the output of "compile" rule matches the expected file.
+write_source_files(
+    name = "test",
+    files = {
+        "expected.js": ":in.js",
+        "expected.js.map": ":in.js.map",
+    },
+)
+
+# Assert that the output of "compile_subdir" rule matches the expected file.
+write_source_files(
+    name = "test_subdir",
+    files = {
+        "expected_subdir.js": ":subdir.js",
+        "expected_subdir.js.map": ":subdir.js.map",
+    },
+)

examples/source_root/in.ts

@@ -0,0 +1 @@
+export const a: string = "foo";

examples/source_root/src/subdir.ts

@@ -0,0 +1 @@
+export const a: string = "a";

swc/private/swc.bzl

@@ -23,10 +23,18 @@ _attrs = {
         """,
     ),
     "source_maps": attr.string(
-        doc = "see https://swc.rs/docs/usage/cli#--source-maps--s",
+        doc = """Create source map files for emitted JavaScript files.
+
+        see https://swc.rs/docs/usage/cli#--source-maps--s""",
         values = ["true", "false", "inline", "both"],
         default = "false",
     ),
+    "source_root": attr.string(
+        doc = """Specify the root path for debuggers to find the reference source code.
+
+        see https://swc.rs/docs/usage/cli#--source-root""",
+        default = "",
+    ),
     "output_dir": attr.bool(
         doc = """Whether to produce a directory output rather than individual files.
 
@@ -247,7 +255,7 @@ def _impl(ctx):
         for src in ctx.files.srcs:
             src_args = ctx.actions.args()
             src_args.add("--source-file-name", src.basename)
-            src_args.add("--source-root", src.dirname)
+            src_args.add("--source-root", src.dirname if ctx.attr.source_root == "" else ctx.attr.source_root)
 
             src_path = _relative_to_package(src.path, ctx)