[jhbuild] sysdeps: Refactor to not instantiate systeminstall unless we sysdeps --install

[Colin Walters <walters src gnome org>]

commit b7e88abcec8c293beaccd17f622eb06cbaa05a89
Author: Colin Walters <walters verbum org>
Date:   Fri Jul 29 11:44:27 2011 -0400

    sysdeps: Refactor to not instantiate systeminstall unless we sysdeps --install
    
    This makes the core work on Ubuntu even if we don't have a backend.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=655546

 jhbuild/commands/sysdeps.py    |    8 +++---
 jhbuild/moduleset.py           |    4 +-
 jhbuild/utils/systeminstall.py |   45 +++++++++++++++++++--------------------
 3 files changed, 28 insertions(+), 29 deletions(-)
---
diff --git a/jhbuild/commands/sysdeps.py b/jhbuild/commands/sysdeps.py
index 7f8e66b..e7a525c 100644
--- a/jhbuild/commands/sysdeps.py
+++ b/jhbuild/commands/sysdeps.py
@@ -47,10 +47,6 @@ class cmd_sysdeps(cmd_build):
     def run(self, config, options, args, help=None):
         config.set_from_cmdline_options(options)
 
-        installer = SystemInstall.find_best()
-        if installer is None:
-            raise FatalError(_("Don't know how to install packages on this system"))
-
         if not config.partial_build:
             raise FatalError(_("Partial build is not enabled; add partial_build = True to ~/.jhbuildrc"))
 
@@ -93,6 +89,10 @@ class cmd_sysdeps(cmd_build):
             print _('  (none)')
 
         if options.install:
+            installer = SystemInstall.find_best()
+            if installer is None:
+                raise FatalError(_("Don't know how to install packages on this system"))
+
             if len(uninstalled) == 0:
                 logging.info(_("No uninstalled system dependencies to install for modules: %r" % (modules, )))
             else:
diff --git a/jhbuild/moduleset.py b/jhbuild/moduleset.py
index 3c214b8..411ac82 100644
--- a/jhbuild/moduleset.py
+++ b/jhbuild/moduleset.py
@@ -40,7 +40,7 @@ from jhbuild.utils import packagedb
 from jhbuild.utils.cmds import compare_version, get_output
 from jhbuild.modtypes.testmodule import TestModule
 from jhbuild.versioncontrol.tarball import TarballBranch
-from jhbuild.utils.systeminstall import SystemInstall
+from jhbuild.utils import systeminstall
 
 __all__ = ['load', 'load_tests', 'get_default_repo']
 
@@ -256,7 +256,7 @@ class ModuleSet:
     def get_system_modules(self, modules):
         assert self.config.partial_build
 
-        installed_pkgconfig = SystemInstall.get_installed_pkgconfigs()
+        installed_pkgconfig = systeminstall.get_installed_pkgconfigs()
         
         # pkgconfig -> (required_version, installed_verison)
         module_state = {}
diff --git a/jhbuild/utils/systeminstall.py b/jhbuild/utils/systeminstall.py
index 684ca0d..5fad0bb 100644
--- a/jhbuild/utils/systeminstall.py
+++ b/jhbuild/utils/systeminstall.py
@@ -26,6 +26,28 @@ from StringIO import StringIO
 
 import cmds
 
+def get_installed_pkgconfigs():
+    """Returns a dictionary mapping pkg-config names to their current versions on the system."""
+    env = dict(os.environ)
+    if 'PKG_CONFIG_PATH' in env:
+        del env['PKG_CONFIG_PATH']
+    proc = subprocess.Popen(['pkg-config', '--list-all'], stdout=subprocess.PIPE, env=env, close_fds=True)
+    stdout = proc.communicate()[0]
+    proc.wait()
+    pkgs = []
+    for line in StringIO(stdout):
+        pkg, rest = line.split(None, 1)
+        pkgs.append(pkg)
+    args = ['pkg-config', '--modversion']
+    args.extend(pkgs)
+    proc = subprocess.Popen(args, stdout=subprocess.PIPE, close_fds=True)
+    stdout = proc.communicate()[0]
+    proc.wait()
+    pkgversions = {}
+    for pkg,verline in zip(pkgs, StringIO(stdout)):
+        pkgversions[pkg] = verline.strip()
+    return pkgversions
+
 class SystemInstall(object):
     def __init__(self):
         pass
@@ -35,29 +57,6 @@ class SystemInstall(object):
         raise NotImplementedError()
 
     @classmethod
-    def get_installed_pkgconfigs(cls):
-        """Returns a dictionary mapping pkg-config names to their current versions on the system."""
-        env = dict(os.environ)
-        if 'PKG_CONFIG_PATH' in env:
-            del env['PKG_CONFIG_PATH']
-        proc = subprocess.Popen(['pkg-config', '--list-all'], stdout=subprocess.PIPE, env=env, close_fds=True)
-        stdout = proc.communicate()[0]
-        proc.wait()
-        pkgs = []
-        for line in StringIO(stdout):
-            pkg, rest = line.split(None, 1)
-            pkgs.append(pkg)
-        args = ['pkg-config', '--modversion']
-        args.extend(pkgs)
-        proc = subprocess.Popen(args, stdout=subprocess.PIPE, close_fds=True)
-        stdout = proc.communicate()[0]
-        proc.wait()
-        pkgversions = {}
-        for pkg,verline in zip(pkgs, StringIO(stdout)):
-            pkgversions[pkg] = verline.strip()
-        return pkgversions
-
-    @classmethod
     def find_best(cls):
         global _classes
         for possible_cls in _classes: