feat: add support for Label in nodejs_binary#entry_point

Fixes bazel-contrib#32

internal/jasmine_node_test/jasmine_node_test.bzl

@@ -60,7 +60,7 @@ def jasmine_node_test(
     all_data += [Label("//internal/jasmine_node_test:jasmine_runner.js")]
     all_data += [":%s_devmode_srcs.MF" % name]
     all_data += [Label("@bazel_tools//tools/bash/runfiles")]
-    entry_point = "build_bazel_rules_nodejs/internal/jasmine_node_test/jasmine_runner.js"
+    entry_point = "//internal/jasmine_node_test:jasmine_runner.js"
 
     nodejs_test(
         name = name,

internal/node/node.bzl

@@ -20,7 +20,7 @@ They support module mapping: any targets in the transitive dependencies with
 a `module_name` attribute can be `require`d by that name.
 """
 
-load("//internal/common:expand_into_runfiles.bzl", "expand_location_into_runfiles")
+load("//internal/common:expand_into_runfiles.bzl", "expand_location_into_runfiles", "expand_path_into_runfiles")
 load("//internal/common:module_mappings.bzl", "module_mappings_runtime_aspect")
 load("//internal/common:node_module_info.bzl", "NodeModuleInfo", "collect_node_modules_aspect")
 load("//internal/common:sources_aspect.bzl", "sources_aspect")
@@ -74,6 +74,11 @@ def _write_loader_script(ctx):
             "node_modules",
         ] if f])
 
+    if len(ctx.attr.entry_point.files) != 1:
+        fail("labels in entry_point must contain exactly one file")
+
+    file_path = expand_path_into_runfiles(ctx, ctx.file.entry_point.short_path)
+
     ctx.actions.expand_template(
         template = ctx.file._loader_template,
         output = ctx.outputs.loader,
@@ -82,7 +87,7 @@ def _write_loader_script(ctx):
             "TEMPLATED_bootstrap": "\n  " + ",\n  ".join(
                 ["\"" + d + "\"" for d in ctx.attr.bootstrap],
             ),
-            "TEMPLATED_entry_point": ctx.attr.entry_point,
+            "TEMPLATED_entry_point": file_path,
             "TEMPLATED_gen_dir": ctx.genfiles_dir.path,
             "TEMPLATED_install_source_map_support": str(ctx.attr.install_source_map_support).lower(),
             "TEMPLATED_module_roots": "\n  " + ",\n  ".join(module_mappings),
@@ -191,12 +196,37 @@ _NODEJS_EXECUTABLE_ATTRS = {
         allow_files = True,
         aspects = [sources_aspect, module_mappings_runtime_aspect, collect_node_modules_aspect],
     ),
-    "entry_point": attr.string(
+    "entry_point": attr.label(
         doc = """The script which should be executed first, usually containing a main function.
-        This attribute expects a string starting with the workspace name, so that it's not ambiguous
-        in cases where a script with the same name appears in another directory or external workspace.
+        The `entry_point` accepts a target's name as an entry point. 
+        If the target is a rule, it should produce the JavaScript entry file that will be passed to the nodejs_binary rule). 
+        For example:
+
+        ```
+        filegroup(
+            name = "entry_file",
+            srcs = ["workspace/path/to/entry/file"]
+        )
+        nodejs_binary(
+          name = "my_binary",
+          ...
+          entry_point = ":entry_file",
+        )
+        ```
+
+        If the entry JavaScript file belongs to the same package (as the BUILD file), 
+        you can simply reference it by its relative name to the package directory:
+
+        ```
+        nodejs_binary(
+          name = "my_binary",
+          ...
+          entry_point = ":file.js",
+        )
+        ```
+
         """,
-        mandatory = True,
+        allow_single_file = True,
     ),
     "install_source_map_support": attr.bool(
         doc = """Install the source-map-support package.

internal/node/test/BUILD.bazel

@@ -5,15 +5,15 @@ load("//:defs.bzl", "nodejs_binary")
 nodejs_binary(
     name = "no_deps",
     data = ["no-deps.js"],
-    entry_point = "build_bazel_rules_nodejs/internal/node/test/no-deps",
+    entry_point = ":no-deps.js",
 )
 
 # You can have a nodejs_binary with a node_modules attribute
 # and no fine grained deps
 nodejs_binary(
     name = "has_deps_legacy",
     data = ["has-deps.js"],
-    entry_point = "build_bazel_rules_nodejs/internal/node/test/has-deps",
+    entry_point = ":has-deps",
     node_modules = "@fine_grained_deps_yarn//:node_modules",
 )
 
@@ -25,7 +25,7 @@ nodejs_binary(
         "has-deps.js",
         "@fine_grained_deps_yarn//typescript",
     ],
-    entry_point = "build_bazel_rules_nodejs/internal/node/test/has-deps",
+    entry_point = ":has-deps",
 )
 
 # You can have a nodejs_binary with both a node_modules attribute
@@ -36,6 +36,6 @@ nodejs_binary(
         "has-deps.js",
         "@fine_grained_deps_yarn//typescript",
     ],
-    entry_point = "build_bazel_rules_nodejs/internal/node/test/has-deps",
+    entry_point = ":has-deps",
     node_modules = "@fine_grained_deps_yarn//:node_modules",
 )

internal/npm_install/generate_build_file.js

@@ -714,7 +714,7 @@ filegroup(
       result += `# Wire up the \`bin\` entry \`${name}\`
 nodejs_binary(
     name = "${name}__bin",
-    entry_point = "${pkg._dir}/${path}",
+    entry_point = "//node_modules/${pkg._dir}:${name}",
     install_source_map_support = False,
     data = [":${pkg._name}__pkg"],
 )

internal/npm_install/test/BUILD.bazel

@@ -34,6 +34,6 @@ nodejs_binary(
         "@npm//jasmine",
         "@npm//unidiff",
     ],
-    entry_point = "build_bazel_rules_nodejs/internal/npm_install/test/update_golden.js",
+    entry_point = "//internal/npm_install/test:update_golden.js",
     install_source_map_support = False,
 )

internal/web_package/BUILD.bazel

@@ -21,7 +21,7 @@ filegroup(
 nodejs_binary(
     name = "assembler",
     data = ["assembler.js"],
-    entry_point = "build_bazel_rules_nodejs/internal/web_package/assembler.js",
+    entry_point = "//internal/web_package:assembler.js",
     install_source_map_support = False,
     node_modules = ":node_modules_none",
 )