build: store dependencies as lists

In Python sets are unordered, so iterating them after converting to a list
always leads to different results. The code iterated on them to collect all
the flags to pass to the compiler, and since the order of the flags changed,
waf would rebuild all of the C files. Seems like in Python 2 this worked as
expected by pure chance.

This commit stores the sets as lists, and converts them to sets when the set
operations are needed.

Fixes #363

waftools/dependencies.py

@@ -15,7 +15,7 @@ class Dependency(object):
         self.identifier, self.desc = dependency['name'], dependency['desc']
         self.attributes = self.__parse_attributes__(dependency)
 
-        ctx.env.known_deps.add(self.identifier)
+        known_deps.add(self.identifier)
         for dep_key in ['deps', 'deps_any', 'deps_neg']:
             if dep_key in self.attributes:
                 deps = self.attributes[dep_key]
@@ -127,18 +127,18 @@ def configure(ctx):
         target = "os-{0}".format(ctx.env.DEST_OS)
         ctx.start_msg('Detected target OS:')
         ctx.end_msg(target)
-        ctx.env.known_deps.add(target)
-        ctx.env.satisfied_deps.add(target)
+        ctx.known_deps.add(target)
+        ctx.satisfied_deps.add(target)
 
     ctx.deps_msg = {}
-    ctx.env['known_deps'] = set()
-    ctx.env['satisfied_deps'] = set()
+    ctx.known_deps = set()
+    ctx.satisfied_deps = set()
     __detect_target_os_dependency__(ctx)
 
 @conf
 def ensure_dependency_is_known(ctx, *depnames):
     deps = set([d for d in depnames if not d.startswith('os-')])
-    if not deps <= ctx.env.known_deps:
+    if not deps <= ctx.known_deps:
         raise ConfigurationError(
             "error in dependencies definition: some dependencies in"
             " {0} are unknown.".format(deps))
@@ -146,7 +146,7 @@ def ensure_dependency_is_known(ctx, *depnames):
 
 @conf
 def mark_satisfied(ctx, dependency_identifier):
-    ctx.env.satisfied_deps.add(dependency_identifier)
+    ctx.satisfied_deps.add(dependency_identifier)
 
 @conf
 def add_optional_message(ctx, dependency_identifier, message):
@@ -156,8 +156,8 @@ def add_optional_message(ctx, dependency_identifier, message):
 def parse_dependencies(ctx, dependencies):
     def __check_dependency__(ctx, dependency):
         Dependency(ctx,
-                   ctx.env.known_deps,
-                   ctx.env.satisfied_deps,
+                   ctx.known_deps,
+                   ctx.satisfied_deps,
                    dependency).check()
 
     [__check_dependency__(ctx, dependency) for dependency in dependencies]
@@ -165,7 +165,17 @@ def parse_dependencies(ctx, dependencies):
 @conf
 def dependency_satisfied(ctx, dependency_identifier):
     ctx.ensure_dependency_is_known(dependency_identifier)
-    return dependency_identifier in ctx.env.satisfied_deps
+    return dependency_identifier in ctx.satisfied_deps
+
+@conf
+def store_dependencies_lists(ctx):
+    ctx.env.known_deps     = list(ctx.known_deps)
+    ctx.env.satisfied_deps = list(ctx.satisfied_deps)
+
+@conf
+def unpack_dependencies_lists(ctx):
+    ctx.known_deps     = set(ctx.env.known_deps)
+    ctx.satisfied_deps = set(ctx.env.satisfied_deps)
 
 def filtered_sources(ctx, sources):
     def __source_file__(source):
@@ -178,10 +188,10 @@ def filtered_sources(ctx, sources):
         if dependency.find('!') == 0:
             dependency = dependency.lstrip('!')
             ctx.ensure_dependency_is_known(dependency)
-            return dependency not in ctx.env.satisfied_deps
+            return dependency not in ctx.satisfied_deps
         else:
             ctx.ensure_dependency_is_known(dependency)
-            return dependency in ctx.env.satisfied_deps
+            return dependency in ctx.satisfied_deps
 
     def __unpack_and_check_filter__(source):
         try:
@@ -195,7 +205,7 @@ def filtered_sources(ctx, sources):
 
 def env_fetch(tx):
     def fn(ctx):
-        deps = list(ctx.env.satisfied_deps)
+        deps = ctx.env.satisfied_deps
         lists = [ctx.env[tx(dep)] for dep in deps if (tx(dep) in ctx.env)]
         return [item for sublist in lists for item in sublist]
     return fn

wscript

@@ -755,5 +755,8 @@ def configure(ctx):
     if not ctx.dependency_satisfied('build-date'):
         ctx.env.CFLAGS += ['-DNO_BUILD_TIMESTAMPS']
 
+    ctx.store_dependencies_lists()
+
 def build(ctx):
+    ctx.unpack_dependencies_lists()
     ctx.load('wscript_build')