Explicit outputs for wasm_cc_binary (#1047)

* Explicit outputs for wasm_cc_binary

* Backwards compatibility

* data_runfiles restore

* restore test_bazel.sh

* Using wrong path on accident

* two separate rules for legacy support

* Added name attribute to wasm_cc_binary rule

bazel/emscripten_toolchain/wasm_cc_binary.bzl

@@ -54,11 +54,81 @@ _wasm_transition = transition(
     ],
 )
 
-def _wasm_binary_impl(ctx):
-    args = ctx.actions.args()
-    args.add("--output_path", ctx.outputs.loader.dirname)
-    args.add_all("--archive", ctx.files.cc_target)
+_ALLOW_OUTPUT_EXTNAMES = [
+    ".js",
+    ".wasm",
+    ".wasm.map",
+    ".worker.js",
+    ".js.mem",
+    ".data",
+    ".fetch.js",
+    ".js.symbols",
+    ".wasm.debug.wasm",
+    ".html",
+]
 
+_WASM_BINARY_COMMON_ATTRS = {
+    "backend": attr.string(
+        default = "_default",
+        values = ["_default", "emscripten", "llvm"],
+    ),
+    "cc_target": attr.label(
+        cfg = _wasm_transition,
+        mandatory = True,
+    ),
+    "exit_runtime": attr.bool(
+        default = False,
+    ),
+    "threads": attr.string(
+        default = "_default",
+        values = ["_default", "emscripten", "off"],
+    ),
+    "simd": attr.bool(
+        default = False,
+    ),
+    "_allowlist_function_transition": attr.label(
+        default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
+    ),
+    "_wasm_binary_extractor": attr.label(
+        executable = True,
+        allow_files = True,
+        cfg = "exec",
+        default = Label("@emsdk//emscripten_toolchain:wasm_binary"),
+    ),
+}
+
+def _wasm_cc_binary_impl(ctx):
+    args = ctx.actions.args()
+    cc_target = ctx.attr.cc_target[0]
+
+    for output in ctx.outputs.outputs:
+        valid_extname = False
+        for allowed_extname in _ALLOW_OUTPUT_EXTNAMES:
+            if output.path.endswith(allowed_extname):
+                valid_extname = True
+                break
+        if not valid_extname:
+            fail("Invalid output '{}'. Allowed extnames: {}".format(output.basename, ", ".join(_ALLOW_OUTPUT_EXTNAMES)))
+
+    args.add_all("--archive", ctx.files.cc_target)
+    args.add_joined("--outputs", ctx.outputs.outputs, join_with = ",")
+
+    ctx.actions.run(
+        inputs = ctx.files.cc_target,
+        outputs = ctx.outputs.outputs,
+        arguments = [args],
+        executable = ctx.executable._wasm_binary_extractor,
+    )
+
+    return DefaultInfo(
+        files = depset(ctx.outputs.outputs),
+        # This is needed since rules like web_test usually have a data
+        # dependency on this target.
+        data_runfiles = ctx.runfiles(transitive_files = depset(ctx.outputs.outputs)),
+    )
+
+def _wasm_cc_binary_legacy_impl(ctx):
+    cc_target = ctx.attr.cc_target[0]
     outputs = [
         ctx.outputs.loader,
         ctx.outputs.wasm,
@@ -72,6 +142,11 @@ def _wasm_binary_impl(ctx):
         ctx.outputs.html,
     ]
 
+    args = ctx.actions.args()
+    args.add("--allow_empty_outputs")
+    args.add_all("--archive", ctx.files.cc_target)
+    args.add_joined("--outputs", outputs, join_with = ",")
+
     ctx.actions.run(
         inputs = ctx.files.cc_target,
         outputs = outputs,
@@ -87,7 +162,19 @@ def _wasm_binary_impl(ctx):
         data_runfiles = ctx.runfiles(transitive_files = depset(outputs)),
     )
 
-def _wasm_binary_outputs(name, cc_target):
+_wasm_cc_binary = rule(
+    name = "wasm_cc_binary",
+    implementation = _wasm_cc_binary_impl,
+    attrs = dict(
+        _WASM_BINARY_COMMON_ATTRS,
+        outputs = attr.output_list(
+            allow_empty = False,
+            mandatory = True,
+        ),
+    ),
+)
+
+def _wasm_binary_legacy_outputs(name, cc_target):
     basename = cc_target.name
     basename = basename.split(".")[0]
     outputs = {
@@ -105,6 +192,13 @@ def _wasm_binary_outputs(name, cc_target):
 
     return outputs
 
+_wasm_cc_binary_legacy = rule(
+    name = "wasm_cc_binary",
+    implementation = _wasm_cc_binary_legacy_impl,
+    attrs = _WASM_BINARY_COMMON_ATTRS,
+    outputs = _wasm_binary_legacy_outputs,
+)
+
 # Wraps a C++ Blaze target, extracting the appropriate files.
 #
 # This rule will transition to the emscripten toolchain in order
@@ -113,36 +207,10 @@ def _wasm_binary_outputs(name, cc_target):
 # Args:
 #   name: The name of the rule.
 #   cc_target: The cc_binary or cc_library to extract files from.
-wasm_cc_binary = rule(
-    implementation = _wasm_binary_impl,
-    attrs = {
-        "backend": attr.string(
-            default = "_default",
-            values = ["_default", "emscripten", "llvm"],
-        ),
-        "cc_target": attr.label(
-            cfg = _wasm_transition,
-            mandatory = True,
-        ),
-        "exit_runtime": attr.bool(
-            default = False,
-        ),
-        "threads": attr.string(
-            default = "_default",
-            values = ["_default", "emscripten", "off"],
-        ),
-        "simd": attr.bool(
-            default = False,
-        ),
-        "_allowlist_function_transition": attr.label(
-            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
-        ),
-        "_wasm_binary_extractor": attr.label(
-            executable = True,
-            allow_files = True,
-            cfg = "exec",
-            default = Label("@emsdk//emscripten_toolchain:wasm_binary"),
-        ),
-    },
-    outputs = _wasm_binary_outputs,
-)
+def wasm_cc_binary(outputs = None, **kwargs):
+    # for backwards compatibility if no outputs are set the deprecated
+    # implementation is used.
+    if not outputs:
+        _wasm_cc_binary_legacy(**kwargs)
+    else:
+        _wasm_cc_binary(outputs = outputs, **kwargs)