Nextjs build to support invocation from another Bazel Workspace

contrib/nextjs/defs.bzl

@@ -58,6 +58,21 @@ _next_build_config = "next.config.mjs"
 # A label to the rules_js/contrib config file.
 _next_standalone_config = Label("next.bazel.mjs")
 
+def _nextjs_compute_chdir():
+    """Compute a chdir that works for main and external workspaces.
+
+    Returns a path under the Bazel output tree that points to this package
+    whether the target is in the main workspace or in an external repository.
+    """
+    repo = native.repo_name()
+    pkg = native.package_name()
+    if repo:
+        if pkg:
+            return "external/{}/{}".format(repo, pkg)
+        else:
+            return "external/{}".format(repo)
+    return pkg
+
 def nextjs(
         name,
         srcs,
@@ -201,7 +216,7 @@ def nextjs_build(name, config, srcs, next_js_binary, data = [], **kwargs):
         args = ["build"],
         srcs = srcs + data + [config],
         out_dirs = [_next_build_out],
-        chdir = native.package_name(),
+        chdir = _nextjs_compute_chdir(),
         mnemonic = "NextJs",
         progress_message = "Compile Next.js app %{label}",
         **kwargs
@@ -233,7 +248,7 @@ def nextjs_start(name, config, app, next_js_binary, data = [], **kwargs):
         tool = next_js_binary,
         args = ["start"],
         data = data + [app, config],
-        chdir = native.package_name(),
+        chdir = _nextjs_compute_chdir(),
         **kwargs
     )
 
@@ -262,7 +277,7 @@ def nextjs_dev(name, config, srcs, data, next_js_binary, **kwargs):
         tool = next_js_binary,
         args = ["dev"],
         data = srcs + data + [config],
-        chdir = native.package_name(),
+        chdir = _nextjs_compute_chdir(),
         **kwargs
     )
 
@@ -313,7 +328,7 @@ def nextjs_standalone_build(name, config, srcs, next_js_binary, data = [], **kwa
         args = ["build"],
         srcs = srcs + data + [":_%s.standalone_config_file" % name, config],
         out_dirs = [_next_build_out],
-        chdir = native.package_name(),
+        chdir = _nextjs_compute_chdir(),
         mnemonic = "NextJs",
         progress_message = "Compile Next.js standalone app %{label}",
         **kwargs
@@ -358,7 +373,7 @@ def nextjs_standalone_server(name, app, pkg = None, data = [], **kwargs):
     js_binary(
         name = name,
         entry_point = ":_{}.js".format(name),
-        chdir = native.package_name(),
+        chdir = _nextjs_compute_chdir(),
         data = data,
         **kwargs
     )

contrib/nextjs/next.bazel.mjs

@@ -12,6 +12,10 @@ if (nextjsStandaloneConfig.startsWith(process.env.BAZEL_BINDIR)) {
         process.env.BAZEL_BINDIR.length + 1
     )
 }
+
+// Support invocation from another workspace: strip "external/<repo>/" if present
+nextjsStandaloneConfig = nextjsStandaloneConfig.replace(/^external\/[^/]+\//, '')
+
 if (!nextjsStandaloneConfig.startsWith(bazelPackage)) {
     throw new Error(
         `Next.js config must be relative to the app root: ${nextjsStandaloneConfig}`