Bug 1322025 - Provide variants of host and target that depend on --help. r=chmanchester

We want to avoid giving --help dependencies to host and target, so that
they we don't spawn config.guess and config.sub when running configure
--help, and don't need to reach out to the which module to find a
suitable shell to execute them.

So, when --help is given, we return a fake host/target namespace, and
avoid the config.guess/config.sub-invoking code being executed.

Then, by giving the --help option to the linter, it can properly find
that the config.guess/config.sub-invoking code doesn't need the
dependency on --help.

This effectively unbreaks configure --help after bug 1313306.

--HG--
extra : rebase_source : 9ed4cbe5a81121b139d0d86aff6af542c2dff53b

build/moz.configure/init.configure

@@ -417,6 +417,23 @@ def split_triplet(triplet):
     )
 
 
+# This defines a fake target/host namespace for when running with --help
+@depends('--help')
+def help_host_target(help):
+    if help:
+        return namespace(
+            alias='unknown-unknown-unknown',
+            cpu='unknown',
+            bitness='unknown',
+            kernel='unknown',
+            os='unknown',
+            endianness='unknown',
+            raw_cpu='unknown',
+            raw_os='unknown',
+            toolchain='unknown-unknown',
+        )
+
+
 @imports('subprocess')
 def config_sub(shell, triplet):
     config_sub = os.path.join(os.path.dirname(__file__), '..',
@@ -437,6 +454,8 @@ def host(value, shell):
 
     return split_triplet(config_sub(shell, host))
 
+host = help_host_target | host
+
 
 @depends('--target', host, shell)
 @checking('for target system type', lambda t: t.alias)
@@ -445,6 +464,8 @@ def target(value, host, shell):
         return host
     return split_triplet(config_sub(shell, value[0]))
 
+target = help_host_target | target
+
 
 @depends(host, target)
 @checking('whether cross compiling')

python/mozbuild/mozbuild/configure/__init__.py

@@ -148,8 +148,8 @@ class CombinedDependsFunction(DependsFunction):
 
     @memoize
     def result(self, need_help_dependency=False):
-        resolved_args = [self.sandbox._value_for(d, need_help_dependency)
-                         for d in self.dependencies]
+        resolved_args = (self.sandbox._value_for(d, need_help_dependency)
+                         for d in self.dependencies)
         return self._func(resolved_args)
 
     def __eq__(self, other):

python/mozbuild/mozbuild/test/configure/lint.py

@@ -57,7 +57,7 @@ class Lint(unittest.TestCase):
             'OLD_CONFIGURE': os.path.join(topsrcdir, 'old-configure'),
             'MOZCONFIG': os.path.join(os.path.dirname(test_path), 'data',
                                       'empty_mozconfig'),
-        }, ['--enable-project=%s' % project])
+        }, ['--enable-project=%s' % project, '--help'])
         sandbox.run(os.path.join(topsrcdir, 'moz.configure'))