[feat] Explain egg dependencies when an egg fails to install

src/zc/buildout/easy_install.py

@@ -242,6 +242,10 @@ def dist_needs_pkg_resources(dist):
     )
 
 
+_doing_list = type('', (), {'__mod__': staticmethod(
+    lambda x: '\n    '.join(*x))})()
+
+
 class Installer(object):
 
     _versions = {}
@@ -696,6 +700,7 @@ class Installer(object):
     def install(self, specs, working_set=None):
 
         logger.debug('Installing %s.', repr(specs)[1:-1])
+        __doing__ = _doing_list, self._requirements_and_constraints
         self._requirements_and_constraints.append(
             "Base installation request: %s" % repr(specs)[1:-1])
 

src/zc/buildout/tests/allow-unknown-extras.txt

@@ -40,6 +40,7 @@ Now we can run the buildout and see that it fails:
     ...
     While:
       Installing eggs.
+      Base installation request: 'allowdemo[bad_extra]'
     Error: Couldn't find the required extra...
 
 If we flip the option on, the buildout succeeds

src/zc/buildout/tests/allowhosts.txt

@@ -61,6 +61,8 @@ Now we can run the buildout and make sure all attempts to dist.plone.org fails::
     ...
     While:
       Installing eggs.
+      Base installation request: 'allowdemo'
+        Requirement of allowdemo: kss.core
       Getting distribution for 'kss.core'.
     Error: Couldn't find a distribution for 'kss.core'.
 
@@ -92,6 +94,8 @@ Now we can run the buildout and make sure all attempts to dist.plone.org fails::
     ...
     While:
       Installing eggs.
+      Base installation request: 'allowdemo'
+        Requirement of allowdemo: kss.core
       Getting distribution for 'kss.core'.
     Error: Couldn't find a distribution for 'kss.core'.
 

src/zc/buildout/tests/dependencylinks.txt

@@ -87,6 +87,8 @@ buildout to see where the egg comes from this time.
     ...
     While:
       Updating eggs.
+      Base installation request: 'depdemo'
+        Requirement of depdemo: demoneeded
       Getting distribution for 'demoneeded'.
     Error: Couldn't find a distribution for 'demoneeded'.
 

src/zc/buildout/tests/repeatable.txt

@@ -207,6 +207,7 @@ versions:
       Getting section foo.
       Initializing section foo.
       Installing recipe spam.
+      Base installation request: 'spam'
       Getting distribution for 'spam'.
     Error: Picked: spam = 2
     ...

src/zc/buildout/tests/test_all.py

@@ -433,6 +433,9 @@ Now, let's create a buildout that requires y and z:
       Requirement of sampley: demoneeded==1.0
     While:
       Installing eggs.
+      Base installation request: 'sampley', 'samplez'
+        Requirement of samplez: demoneeded==1.1
+        Requirement of sampley: demoneeded==1.0
     Error: There is a version conflict.
     We already have: demoneeded 1.1
     but sampley 1 requires 'demoneeded==1.0'.
@@ -483,6 +486,12 @@ If we use the verbose switch, we can see where requirements are coming from:
       Requirement of sampley: demoneeded==1.0
     While:
       Installing eggs.
+      Base installation request: 'samplea', 'samplez'
+        Requirement of samplez: demoneeded==1.1
+        Requirement of samplea: sampleb
+        Requirement of sampleb: samplea
+        Requirement of sampleb: sampley
+        Requirement of sampley: demoneeded==1.0
     Error: There is a version conflict.
     We already have: demoneeded 1.1
     but sampley 1 requires 'demoneeded==1.0'.
@@ -551,6 +560,11 @@ that we can't find. when run in verbose mode
     ...
     While:
       Installing eggs.
+      Base installation request: 'samplea'
+        Requirement of samplea: sampleb
+        Requirement of sampleb: samplea
+        Requirement of sampleb: sampley
+        Requirement of sampley: demoneeded
       Getting distribution for 'demoneeded'.
     Error: Couldn't find a distribution for 'demoneeded'.
     """
@@ -2216,6 +2230,28 @@ def dealing_with_extremely_insane_dependencies():
     ...
     While:
       Installing pack1.
+      Base installation request: 'pack0'
+        Requirement of pack0: pack4
+        Requirement of pack0: pack3
+        Requirement of pack0: pack2
+        Requirement of pack0: pack1
+        Requirement of pack4: pack5
+        Requirement of pack4: pack3
+        Requirement of pack4: pack2
+        Requirement of pack4: pack1
+        Requirement of pack4: pack0
+        Requirement of pack3: pack4
+        Requirement of pack3: pack2
+        Requirement of pack3: pack1
+        Requirement of pack3: pack0
+        Requirement of pack2: pack4
+        Requirement of pack2: pack3
+        Requirement of pack2: pack1
+        Requirement of pack2: pack0
+        Requirement of pack1: pack4
+        Requirement of pack1: pack3
+        Requirement of pack1: pack2
+        Requirement of pack1: pack0
       Getting distribution for 'pack5'.
     Error: Couldn't find a distribution for 'pack5'.
 
@@ -2257,6 +2293,28 @@ def dealing_with_extremely_insane_dependencies():
     ...
     While:
       Installing pack1.
+      Base installation request: 'pack0'
+        Requirement of pack0: pack4
+        Requirement of pack0: pack3
+        Requirement of pack0: pack2
+        Requirement of pack0: pack1
+        Requirement of pack4: pack5
+        Requirement of pack4: pack3
+        Requirement of pack4: pack2
+        Requirement of pack4: pack1
+        Requirement of pack4: pack0
+        Requirement of pack3: pack4
+        Requirement of pack3: pack2
+        Requirement of pack3: pack1
+        Requirement of pack3: pack0
+        Requirement of pack2: pack4
+        Requirement of pack2: pack3
+        Requirement of pack2: pack1
+        Requirement of pack2: pack0
+        Requirement of pack1: pack4
+        Requirement of pack1: pack3
+        Requirement of pack1: pack2
+        Requirement of pack1: pack0
       Getting distribution for 'pack5'.
     Error: Couldn't find a distribution for 'pack5'.
     """
@@ -3301,6 +3359,7 @@ def want_new_zcrecipeegg():
       Getting section egg.
       Initializing section egg.
       Installing recipe zc.recipe.egg <2dev.
+      Base installation request: 'zc.recipe.egg <2dev'
       Getting distribution for 'zc.recipe.egg<2dev,>=2.0.6'.
     Error: Couldn't find a distribution for 'zc.recipe.egg<2dev,>=2.0.6'.
     """