[feat] Add dependencies in __buildout_signature__

Add referred parts' hash strings in __buildout_signature__, that
invokes rebuild of a part when one of its (recursive) dependencies
are modified.

Also remove duplicates and sort entries in __buildout_signature__.

src/zc/buildout/buildout.py

@@ -465,6 +465,8 @@ class Buildout(DictMixin):
         self._raw = _unannotate(data)
         self._data = {}
         self._parts = []
+        self._initializing = []
+        self._signature_cache = {}
 
         # provide some defaults before options are parsed
         # because while parsing options those attributes might be
@@ -824,9 +826,7 @@ class Buildout(DictMixin):
                 _save_options(section, self[section], sys.stdout)
             print_()
 
-
-        # compute new part recipe signatures
-        self._compute_part_signatures(install_parts)
+        del self._signature_cache
 
         # uninstall parts that are no-longer used or who's configs
         # have changed
@@ -1024,17 +1024,6 @@ class Buildout(DictMixin):
                 self._logger.warning(
                     "Unexpected entry, %r, in develop-eggs directory.", f)
 
-    def _compute_part_signatures(self, parts):
-        # Compute recipe signature and add to options
-        for part in parts:
-            options = self.get(part)
-            if options is None:
-                options = self[part] = {}
-            recipe, entry = _recipe(options)
-            req = pkg_resources.Requirement.parse(recipe)
-            sig = _dists_sig(pkg_resources.working_set.resolve([req]))
-            options['__buildout_signature__'] = ' '.join(sig)
-
     def _read_installed_part_options(self):
         old = self['buildout']['installed']
         if old and os.path.isfile(old):
@@ -1413,21 +1402,44 @@ class Buildout(DictMixin):
                     v = v.replace(os.getcwd(), base_path)
                 print_("%s =%s" % (k, v))
 
-    def __getitem__(self, section):
-        __doing__ = 'Getting section %s.', section
+    def initialize(self, options, reqs, entry):
+        recipe_class = _install_and_load(reqs, 'zc.buildout', entry, self)
         try:
-            return self._data[section]
+            sig = self._signature_cache[reqs]
         except KeyError:
-            pass
+            req = pkg_resources.Requirement.parse(reqs)
+            sig = self._signature_cache[reqs] = sorted(set(
+                _dists_sig(pkg_resources.working_set.resolve([req]))))
+        self._initializing.append((options, sig))
+        try:
+            recipe = recipe_class(self, options.name, options)
+            options['__buildout_signature__']
+        finally:
+            del self._initializing[-1]
+        return recipe
 
+    def __getitem__(self, section):
+        __doing__ = 'Getting section %s.', section
         try:
-            data = self._raw[section]
+            options = self._data[section]
         except KeyError:
-            raise MissingSection(section)
-
-        options = self.Options(self, section, data)
-        self._data[section] = options
-        options._initialize()
+            try:
+                data = self._raw[section]
+            except KeyError:
+                raise MissingSection(section)
+
+            options = self.Options(self, section, data)
+            self._data[section] = options
+            options._initialize()
+
+        if self._initializing:
+            caller = self._initializing[-1][0]
+            if 'buildout' != section and not (
+                  section in caller.depends or
+                  # Do not only check the caller,
+                  # because of circular dependencies during substitutions.
+                  section in (x[0].name for x in self._initializing)):
+                caller.depends.add(section)
         return options
 
     def __setitem__(self, name, data):
@@ -1510,6 +1522,7 @@ class Options(DictMixin):
         self._raw = data
         self._cooked = {}
         self._data = {}
+        self.depends = set()
 
     def _initialize(self):
         name = self.name
@@ -1531,16 +1544,15 @@ class Options(DictMixin):
             self.buildout[dname]
 
         if self.get('recipe'):
-            self.initialize()
+            self.recipe = self.buildout.initialize(self, *_recipe(self._data))
             self.buildout._parts.append(name)
 
-    def initialize(self):
-        reqs, entry = _recipe(self._data)
-        buildout = self.buildout
-        recipe_class = _install_and_load(reqs, 'zc.buildout', entry, buildout)
-
-        name = self.name
-        self.recipe = recipe_class(buildout, name, self)
+        m = md5()
+        # access values through .get() instead of .items() to detect unused keys
+        for key in sorted(self.keys()):
+            value = self._data.get(key, self._cooked.get(key, self._raw.get(key)))
+            m.update(('%r\0%r\0' % (key, value)).encode())
+        self.items_signature = '%s:%s' % (name, m.hexdigest())
 
     def _do_extend_raw(self, name, data, doing):
         if name == 'buildout':
@@ -1593,6 +1605,16 @@ class Options(DictMixin):
         if v is None:
             v = self._raw.get(option)
             if v is None:
+                if option == '__buildout_signature__':
+                    buildout = self.buildout
+                    options, sig = buildout._initializing[-1]
+                    if options is self:
+                        self.depends = frozenset(self.depends)
+                        v = self._data[option] = ' '.join(sig + [
+                            buildout[dependency].items_signature
+                            for dependency in sorted(self.depends)])
+                        return v
+                    raise zc.buildout.UserError("premature access to " + option)
                 return default
 
         __doing__ = 'Getting option %s:%s.', self.name, option
@@ -1648,7 +1670,14 @@ class Options(DictMixin):
             section, option = s
             if not section:
                 section = self.name
-            v = self.buildout[section].get(option, None, seen, last=last)
+                options = self
+            else:
+                self.buildout._initializing.append((self,))
+                try:
+                    options = self.buildout[section]
+                finally:
+                    del self.buildout._initializing[-1]
+            v = options.get(option, None, seen, last=last)
             if v is None:
                 if option == '_buildout_section_name_':
                     v = self.name

src/zc/buildout/testing.py

@@ -222,6 +222,9 @@ class Buildout(zc.buildout.buildout.Buildout):
 
     Options = TestOptions
 
+    def initialize(self, *args):
+        pass
+
 def buildoutSetUp(test):
 
     test.globs['__tear_downs'] = __tear_downs = []

src/zc/buildout/tests/buildout.txt

@@ -2700,7 +2700,7 @@ were created.
 The ``.installed.cfg`` is only updated for the recipes that ran::
 
     >>> cat(sample_buildout, '.installed.cfg')
-    ... # doctest: +NORMALIZE_WHITESPACE
+    ... # doctest: +NORMALIZE_WHITESPACE +ELLIPSIS
     [buildout]
     installed_develop_eggs = /sample-buildout/develop-eggs/recipes.egg-link
     parts = debug d1 d2 d3 d4
@@ -2730,7 +2730,7 @@ The ``.installed.cfg`` is only updated for the recipes that ran::
     <BLANKLINE>
     [d4]
     __buildout_installed__ = /sample-buildout/data2-extra
-    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg==
+    __buildout_signature__ = recipes-PiIFiO8ny5yNZ1S3JfT0xg== d2:...
     path = /sample-buildout/data2-extra
     recipe = recipes:mkdir
 

src/zc/buildout/tests/test_all.py

@@ -2261,6 +2261,82 @@ def dealing_with_extremely_insane_dependencies():
     Error: Couldn't find a distribution for 'pack5'.
     """
 
+def test_part_pulled_by_recipe():
+    """
+    >>> mkdir(sample_buildout, 'recipes')
+    >>> write(sample_buildout, 'recipes', 'test.py',
+    ... '''
+    ... class Recipe:
+    ...
+    ...     def __init__(self, buildout, name, options):
+    ...         self.x = buildout[options['x']][name]
+    ...
+    ...     def install(self):
+    ...         print(self.x)
+    ...         return ()
+    ...
+    ...     update = install
+    ... ''')
+
+
+    >>> write(sample_buildout, 'recipes', 'setup.py',
+    ... '''
+    ... from setuptools import setup
+    ... setup(
+    ...     name = "recipes",
+    ...     entry_points = {'zc.buildout': ['test = test:Recipe']},
+    ...     )
+    ... ''')
+
+    >>> write(sample_buildout, 'buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... develop = recipes
+    ... parts = a
+    ... [a]
+    ... recipe = recipes:test
+    ... x = b
+    ... [b]
+    ... <= a
+    ... a = A
+    ... b = B
+    ... c = ${c:x}
+    ... [c]
+    ... x = c
+    ... ''')
+
+    >>> os.chdir(sample_buildout)
+    >>> buildout = os.path.join(sample_buildout, 'bin', 'buildout')
+
+    >>> print_(system(buildout), end='')
+    Develop: '/sample-buildout/recipes'
+    Installing b.
+    B
+    Section `b` contains unused option(s): 'c'.
+    This may be an indication for either a typo in the option's name or a bug in the used recipe.
+    Installing a.
+    A
+
+    >>> print_(system(buildout), end='')
+    Develop: '/sample-buildout/recipes'
+    Updating b.
+    B
+    Updating a.
+    A
+
+    >>> cat('.installed.cfg') # doctest: +ELLIPSIS
+    [buildout]
+    ...
+    [b]
+    __buildout_installed__ = 
+    __buildout_signature__ = recipes-... c:...
+    ...
+    [a]
+    __buildout_installed__ = 
+    __buildout_signature__ = recipes-... b:...
+    ...
+    """
+
 def read_find_links_to_load_extensions():
     r"""
 We'll create a wacky buildout extension that just announces itself when used:

zc.recipe.egg_/src/zc/recipe/egg/api.rst

@@ -97,14 +97,14 @@ of extra requirements to be included in the working set.
 We can see that the options were augmented with additional data
 computed by the egg recipe by looking at .installed.cfg:
 
-    >>> cat(sample_buildout, '.installed.cfg')
+    >>> cat(sample_buildout, '.installed.cfg') # doctest: +ELLIPSIS
     [buildout]
     installed_develop_eggs = /sample-buildout/develop-eggs/sample.egg-link
     parts = sample-part
     <BLANKLINE>
     [sample-part]
     __buildout_installed__ = 
-    __buildout_signature__ = ...
+    __buildout_signature__ = sample-... setuptools-... zc.buildout-... zc.recipe.egg-...
     _b = /sample-buildout/bin
     _d = /sample-buildout/develop-eggs
     _e = /sample-buildout/eggs