fix: handle opaque targets in swc srcs (#110)

examples/custom_outs/BUILD.bazel

@@ -4,12 +4,14 @@ load("@aspect_rules_swc//swc:defs.bzl", "swc_transpiler")
 [
     swc_transpiler(
         name = "transpile_" + format,
-        srcs = ["in.ts"],
+        srcs = ["a.ts"],
         args = [
             "--config",
             "module.type=" + format,
         ],
-        js_outs = [format + "/out." + ("cjs" if format == "commonjs" else "js")],
+        # The extension of the outputs can be modified using js_outs
+        js_outs = [format + "/a." + ("cjs" if format == "commonjs" else "js")],
+        out_dir = format,
     )
     for format in [
         "commonjs",
@@ -20,7 +22,7 @@ load("@aspect_rules_swc//swc:defs.bzl", "swc_transpiler")
 write_source_files(
     name = "tests",
     files = {
-        "expected.cjs": ":commonjs/out.cjs",
-        "expected.js": ":es6/out.js",
+        "expected.cjs": ":commonjs/a.cjs",
+        "expected.js": ":es6/a.js",
     },
 )

examples/custom_outs/expected.cjs

@@ -7,4 +7,4 @@ var a = "a";
 exports.a = a;
 
 
-//# sourceMappingURL=out.cjs.map
+//# sourceMappingURL=a.cjs.map

examples/opaque_src/BUILD.bazel

@@ -0,0 +1,34 @@
+"""Simple use case for swc: transpiling TypeScript using the `swc` rule
+
+Note that this example also depends on the setup in /WORKSPACE at the root of this repository.
+"""
+
+load("@aspect_bazel_lib//lib:write_source_files.bzl", "write_source_files")
+load("@aspect_bazel_lib//lib:output_files.bzl", "output_files")
+load("@aspect_rules_swc//swc:defs.bzl", "swc")
+
+filegroup(
+    name = "opaque_src",
+    srcs = ["in.ts"],
+)
+
+# In this case we pass a target containing sources so the swc macro can't pre-declare the .js output targets
+swc(
+    name = "transpile",
+    srcs = [":opaque_src"],
+)
+
+# But we can extract the opaque outputs using output_files to make a friendly label for the output .js file
+output_files(
+    name = "in.js",
+    paths = ["%s/in.js" % package_name()],
+    target = ":transpile",
+)
+
+# Assert that the output of "transpile" rule matches the expected file.
+write_source_files(
+    name = "test",
+    # This is a pre-declared output of the "transpile" rule, so we can refer to it directly using a Bazel label
+    # even though the file itself is generated by Bazel in ../../bazel-bin/examples/simple/in.js
+    files = {"expected.js": ":in.js"},
+)

examples/opaque_src/in.ts

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

swc/defs.bzl

@@ -68,7 +68,7 @@ def swc(name, srcs = None, args = [], data = [], output_dir = False, swcrc = Non
 
     if not output_dir:
         js_outs = _swc_lib.calculate_js_outs(srcs, out_dir)
-        map_outs = _swc_lib.calculate_map_outs(srcs, out_dir, source_maps)
+        map_outs = _swc_lib.calculate_map_outs(srcs, source_maps, out_dir)
 
     swc_transpiler(
         name = name,

swc/private/swc.bzl

@@ -53,9 +53,6 @@ _SUPPORTED_EXTENSIONS = [".ts", ".tsx", ".jsx", ".mjs", ".cjs", ".js"]
 def _is_supported_src(src):
     return paths.split_extension(src)[-1] in _SUPPORTED_EXTENSIONS
 
-def _declare_outputs(ctx, paths):
-    return [ctx.actions.declare_file(p) for p in paths]
-
 # TODO: aspect_bazel_lib should provide this?
 def _relative_to_package(path, ctx):
     for prefix in (ctx.bin_dir.path, ctx.label.package):
@@ -64,6 +61,21 @@ def _relative_to_package(path, ctx):
             path = path[len(prefix):]
     return path
 
+def _calculate_js_out(src, out_dir = None, js_outs = []):
+    if not _is_supported_src(src):
+        return None
+    js_out = paths.replace_extension(src, ".js")
+    if out_dir:
+        js_out = paths.join(out_dir, js_out)
+
+    # Check if a custom out was requested with a potentially different extension
+    for maybe_out in js_outs:
+        no_ext = paths.replace_extension(js_out, "")
+        if no_ext == paths.replace_extension(maybe_out, ""):
+            js_out = maybe_out
+            break
+    return js_out
+
 def _calculate_js_outs(srcs, out_dir = None):
     if out_dir == None:
         js_srcs = []
@@ -73,21 +85,20 @@ def _calculate_js_outs(srcs, out_dir = None):
         if len(js_srcs) > 0:
             fail("Detected swc rule with srcs=[{}, ...] and out_dir=None. Please set out_dir when compiling .js files.".format(", ".join(js_srcs[:3])))
 
-    js_outs = [paths.replace_extension(f, ".js") for f in srcs if _is_supported_src(f)]
-    if out_dir != None:
-        js_outs = [paths.join(out_dir, f) for f in js_outs]
-
-    return js_outs
+    return [f2 for f2 in [_calculate_js_out(f, out_dir) for f in srcs] if f2]
 
-def _calculate_map_outs(srcs, out_dir, source_maps):
+def _calculate_map_out(src, source_maps, out_dir = None):
     if source_maps in ["false", "inline"]:
-        return []
+        return None
+    if not _is_supported_src(src):
+        return None
+    map_out = paths.replace_extension(src, ".js.map")
+    if out_dir:
+        map_out = paths.join(out_dir, map_out)
+    return map_out
 
-    map_outs = [paths.replace_extension(f, ".js.map") for f in srcs if _is_supported_src(f)]
-    if out_dir != None:
-        map_outs = [paths.join(out_dir, f) for f in map_outs]
-
-    return map_outs
+def _calculate_map_outs(srcs, source_maps, out_dir = None):
+    return [f2 for f2 in [_calculate_map_out(f, source_maps, out_dir) for f in srcs] if f2]
 
 def _impl(ctx):
     swcinfo = ctx.toolchains["@aspect_rules_swc//swc:toolchain_type"].swcinfo
@@ -129,32 +140,27 @@ def _impl(ctx):
             progress_message = "Transpiling with swc %{label}",
         )
     else:
-        srcs = [_relative_to_package(src.path, ctx) for src in ctx.files.srcs]
+        output_sources = []
 
-        if len(ctx.attr.js_outs):
-            js_outs = ctx.outputs.js_outs
-        else:
-            js_outs = _declare_outputs(ctx, _calculate_js_outs(srcs, ctx.attr.out_dir))
-        if len(ctx.attr.map_outs):
-            map_outs = ctx.outputs.map_outs
-        else:
-            map_outs = _declare_outputs(ctx, _calculate_map_outs(srcs, ctx.attr.out_dir, ctx.attr.source_maps))
+        for src in ctx.files.srcs:
+            inputs = [copy_file_to_bin_action(ctx, src)] + swcinfo.tool_files
 
-        output_sources = js_outs + map_outs
+            src_path = _relative_to_package(src.path, ctx)
+            js_out_path = _calculate_js_out(src_path, ctx.attr.out_dir, [_relative_to_package(f.path, ctx) for f in ctx.outputs.js_outs])
+            if not js_out_path:
+                # This source file is not a supported src
+                continue
+            js_out = ctx.actions.declare_file(js_out_path)
+            outputs = [js_out]
+            map_out_path = _calculate_map_out(src_path, ctx.attr.source_maps, ctx.attr.out_dir)
+            if map_out_path:
+                outputs.append(ctx.actions.declare_file(map_out_path))
 
-        for i, src in enumerate(ctx.files.srcs):
             src_args = ctx.actions.args()
 
-            js_out = js_outs[i]
-            inputs = [copy_file_to_bin_action(ctx, src)] + swcinfo.tool_files
-            outputs = [js_out]
-            if map_outs:
-                outputs.append(map_outs[i])
-
             # Pass in the swcrc config if it is set
             if ctx.file.swcrc:
                 swcrc_path = ctx.file.swcrc.short_path
-                swcrc_directory = paths.dirname(swcrc_path)
                 src_args.add("--config-file", swcrc_path)
                 inputs.append(copy_file_to_bin_action(ctx, ctx.file.swcrc))
             else:
@@ -167,6 +173,8 @@ def _impl(ctx):
                 "-q",
             ])
 
+            output_sources.extend(outputs)
+
             ctx.actions.run(
                 inputs = inputs,
                 arguments = [args, src_args],
@@ -227,6 +235,7 @@ swc = struct(
     attrs = dict(_attrs, **_outputs),
     toolchains = ["@aspect_rules_swc//swc:toolchain_type"],
     SUPPORTED_EXTENSIONS = _SUPPORTED_EXTENSIONS,
+    calculate_js_out = _calculate_js_out,
     calculate_js_outs = _calculate_js_outs,
     calculate_map_outs = _calculate_map_outs,
 )