Add a node_scope option to node_module targets to support package-sco…

…pes (pantsbuild#6616)

This is the implementation of pantsbuild#6540.

### Problem
Pants source-level dependencies for Node.js targets does not support [node-scopes](https://docs.npmjs.com/misc/scope).

### Solution
Add a `node_scope` config to `node_module` targets and a repo-level `node_scope` to `node-distribution`.

### Result
The repo-owner may specify a target-level and/or global node-scope that will resolve all Node.js source-level dependencies under the correct node-scope rules.

For example, if you have a target dependency on **src/node/pants/custom/web-package:web-package** with a package name of `web-package`, the installed path under the `node_modules` directory would be `*/node_modules/web-package`.

If a node_scope=pants is defined for `src/node/pants/custom/web-package:web-package`. Then the installed directory would be `*/node_modules/@pants/web-package`.

Target-level `node_scope` overrides repo-level `node_scope`.

### Defining scope in package.json

When dep inference is ready, a potential update to this implementation is to be able to infer the node_scope from the name defined in package.json.

contrib/node/src/python/pants/contrib/node/subsystems/node_distribution.py

@@ -60,6 +60,8 @@ def register_options(cls, register):
              help='The path to the global eslint ignore path')
     register('--eslint-version', default='4.15.0', fingerprint=True,
              help='Use this ESLint version.')
+    register('--node-scope', advanced=True, fingerprint=True,
+             help='Default node scope for repo. Scope groups related packages together.')
 
   @memoized_method
   def _get_package_managers(self):
@@ -116,6 +118,10 @@ def eslint_config(self):
   def eslint_ignore(self):
     return self.get_options().eslint_ignore
 
+  @memoized_property
+  def node_scope(self):
+    return self.get_options().node_scope
+
   @memoized_method
   def _install_node(self):
     """Install the Node distribution from pants support binaries.

contrib/node/src/python/pants/contrib/node/subsystems/resolvers/npm_resolver.py

@@ -134,23 +134,49 @@ def resolve_target(self, node_task, target, results_dir, node_paths, resolve_loc
           raise TaskError('Failed to resolve dependencies for {}:\n\t{} failed with exit code {}'
                           .format(target.address.reference(), command, result))
         if source_deps:
-          self._link_source_dependencies(target, results_dir, node_paths, source_deps)
-
-  def _link_source_dependencies(self, target, results_dir, node_paths, source_deps):
+          self._link_source_dependencies(node_task, target, results_dir, node_paths, source_deps)
 
+  def _link_source_dependencies(self, node_task, target, results_dir, node_paths, source_deps):
     for package_name, file_path in source_deps.items():
       # Package name should always the same as the target name
       dep = self._get_target_from_package_name(target, package_name, file_path)
+
+      # Apply node-scoping rules if applicable
+      node_scope = dep.payload.node_scope or node_task.node_distribution.node_scope
+      dep_package_name = self._scoped_package_name(node_task, dep.package_name, node_scope)
       # Symlink each target
       dep_path = node_paths.node_path(dep)
       node_module_dir = os.path.join(results_dir, 'node_modules')
-      relative_symlink(dep_path, os.path.join(node_module_dir, dep.package_name))
+      relative_symlink(dep_path, os.path.join(node_module_dir, dep_package_name))
       # If there are any bin, we need to symlink those as well
       bin_dir = os.path.join(node_module_dir, '.bin')
       for bin_name, rel_bin_path in dep.bin_executables.items():
         bin_path = os.path.join(dep_path, rel_bin_path)
         relative_symlink(bin_path, os.path.join(bin_dir, bin_name))
 
+  @staticmethod
+  def _scoped_package_name(node_task, package_name, node_scope):
+    """Apply a node_scope to the package name.
+
+    Overrides any existing package_name if already in a scope
+
+    :return: A package_name with prepended with a node scope via '@'
+    """
+
+    if not node_scope:
+      return package_name
+
+    scoped_package_name = package_name
+    chunk = package_name.split('/', 1)
+    if len(chunk) > 1 and chunk[0].startswith('@'):
+      scoped_package_name = os.path.join('@{}'.format(node_scope), chunk[1:])
+    else:
+      scoped_package_name = os.path.join('@{}'.format(node_scope), package_name)
+
+    node_task.context.log.debug(
+      'Node package "{}" will be resolved with scope "{}".'.format(package_name, scoped_package_name))
+    return scoped_package_name
+
   @staticmethod
   def _emit_package_descriptor(node_task, target, results_dir, node_paths):
     dependencies = {

contrib/node/src/python/pants/contrib/node/targets/node_module.py

@@ -22,8 +22,8 @@ class NodeModule(NodePackage):
 
   def __init__(
     self, package_manager=None, sources=None, build_script=None, output_dir='dist',
-    dev_dependency=False, style_ignore_path='.eslintignore', address=None, payload=None, 
-    bin_executables=None, **kwargs):
+    dev_dependency=False, style_ignore_path='.eslintignore', address=None, payload=None,
+    bin_executables=None, node_scope=None, **kwargs):
     """
     :param sources: Javascript and other source code files that make up this module; paths are
                     relative to the BUILD file's directory.
@@ -49,6 +49,11 @@ def __init__(
                            E.G. { 'app': './cli.js', 'runner': './scripts/run.sh' }
                            `string`, file path and package name as  the default bin name
                            E.G. './cli.js' would be interpreted as { 'app': './cli.js' }
+    :param node_scope: Groups related packages together by adding a scope. The `@`
+      symbol is typically used for specifying scope in the package name in `package.json`.
+      However pants target addresses do not allow for `@` in the target address.
+      A repo-level default scope can be added with the --node-distribution-node-scope option.
+      Any target-level node_scope will override the global node-scope.
 
     """
     # TODO(John Sirois): Support devDependencies, etc.  The devDependencies case is not
@@ -74,6 +79,7 @@ def __init__(
       'dev_dependency': PrimitiveField(dev_dependency),
       'style_ignore_path': PrimitiveField(style_ignore_path),
       'bin_executables': PrimitiveField(bin_executables),
+      'node_scope': PrimitiveField(node_scope),
     })
     super(NodeModule, self).__init__(address=address, payload=payload, **kwargs)