we can produce dehydrated pex files with the --dehydrated flag!

pex/bin/pex.py

@@ -260,6 +260,17 @@ def configure_clp_pex_resolution(parser, builder):
     callback_args=(builder,),
     help='Whether to transitively resolve requirements. Default: True')
 
+  group.add_option(
+    '--dehydrated',
+    dest='dehydrated',
+    default=False,
+    action='callback',
+    callback=parse_bool,
+    help='[EXPERIMENTAL] Whether to avoid adding requirements to the generated pex file and '
+         'instead add an entry to PEX-INFO containing the transitive dependencies of all '
+         'requirements.'
+  )
+
   # Set the pex tool to fetch from PyPI by default if nothing is specified.
   parser.set_default('repos', [PyPIFetcher()])
   parser.add_option_group(group)
@@ -647,8 +658,12 @@ def walk_and_do(fn, src_dir):
       for resolved_dist in resolveds:
         log('  %s -> %s' % (resolved_dist.requirement, resolved_dist.distribution),
             V=options.verbosity)
-        pex_builder.add_distribution(resolved_dist.distribution)
-        pex_builder.add_requirement(resolved_dist.requirement)
+
+        if options.dehydrated:
+          pex_info.add_dehydrated_requirement(resolved_dist.requirement)
+        else:
+          pex_builder.add_distribution(resolved_dist.distribution)
+          pex_builder.add_requirement(resolved_dist.requirement)
     except Unsatisfiable as e:
       die(e)
 

pex/pex_info.py

@@ -26,6 +26,7 @@ class PexInfo(object):
   distributions: {dist_name: str}    # map from distribution name (i.e. path in
                                      # the internal cache) to its cache key (sha1)
   requirements: list                 # list of requirements for this environment
+  dehydrated_requirements: list      # list of requirements to resolve at bootstrap time.
 
   # Environment options
   pex_root: string                    # root of all pex-related files eg: ~/.pex
@@ -67,6 +68,7 @@ def make_build_properties(cls, interpreter=None):
   def default(cls, interpreter=None):
     pex_info = {
       'requirements': [],
+      'dehydrated_requirements': [],
       'distributions': {},
       'build_properties': cls.make_build_properties(interpreter),
     }
@@ -132,6 +134,10 @@ def __init__(self, info=None):
     if not isinstance(requirements, (list, tuple)):
       raise ValueError('Expected requirements to be a list, got %s' % type(requirements))
     self._requirements = OrderedSet(self._parse_requirement_tuple(req) for req in requirements)
+    dehydrated_requirements = self._pex_info.get('dehydrated_requirements', [])
+    if not isinstance(dehydrated_requirements, (list, tuple)):
+      raise ValueError('Expected dehydrated_requirements to be a list, got %s' % type(dehydrated_requirements))
+    self._dehydrated_requirements = OrderedSet(self._parse_requirement_tuple(req) for req in dehydrated_requirements)
 
   def _get_safe(self, key):
     if key not in self._pex_info:
@@ -261,10 +267,17 @@ def script(self, value):
   def add_requirement(self, requirement):
     self._requirements.add(str(requirement))
 
+  def add_dehydrated_requirement(self, requirement):
+    self._dehydrated_requirements.add(str(requirement))
+
   @property
   def requirements(self):
     return self._requirements
 
+  @property
+  def dehydrated_requirements(self):
+    return self._dehydrated_requirements
+
   def add_distribution(self, location, sha):
     self._distributions[location] = sha
 
@@ -307,10 +320,12 @@ def update(self, other):
     self._distributions.update(other.distributions)
     self._interpreter_constraints.update(other.interpreter_constraints)
     self._requirements.update(other.requirements)
+    self._dehydrated_requirements.update(other.dehydrated_requirements)
 
   def dump(self, **kwargs):
     pex_info_copy = self._pex_info.copy()
     pex_info_copy['requirements'] = sorted(self._requirements)
+    pex_info_copy['dehydrated_requirements'] = sorted(self._dehydrated_requirements)
     pex_info_copy['interpreter_constraints'] = sorted(self._interpreter_constraints)
     pex_info_copy['distributions'] = self._distributions.copy()
     return json.dumps(pex_info_copy, **kwargs)

pex/version.py

@@ -1,4 +1,4 @@
 # Copyright 2015 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-__version__ = '1.6.12'
+__version__ = '1.6.12+dehydration'