[gobject-introspection/fix-source-pos-root-fallback: 2/2] scanner: rework source root guessing code

[Christoph Reiter <creiter src gnome org>]

commit ea11f9cb69c61c74a94a7ce645939d861b99d5c2
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Sun Jan 6 14:01:11 2019 +0100

    scanner: rework source root guessing code
    
    commonprefix doesn't work on relative paths and doesn't return directories so
    so for the g-i build case it returned an empty string resulting in paths
    relative to the working directory, making the build not reproducible.
    
    To somehwat improve this make sure the paths are absolute, use commonpath
    and if no common dir can be found just fall back to passing all directories
    so we only write the basenames.
    
    I guess we should look into passing --sources-top-dirs in the g-i build.

 giscanner/scannermain.py | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)
---
diff --git a/giscanner/scannermain.py b/giscanner/scannermain.py
index a2d7ea5d..154fe483 100644
--- a/giscanner/scannermain.py
+++ b/giscanner/scannermain.py
@@ -428,6 +428,7 @@ def create_source_scanner(options, args):
         filenames = extract_filelist(options)
     else:
         filenames = extract_filenames(args)
+    filenames = [os.path.realpath(f) for f in filenames]
 
     if platform.system() == 'Darwin':
         options.cpp_undefines.append('__BLOCKS__')
@@ -490,6 +491,26 @@ def write_output(data, options):
         _error("while writing output: %s" % (e.strerror, ))
 
 
+def get_source_root_dirs(options, filenames):
+    if options.sources_top_dirs:
+        return options.sources_top_dir
+
+    # None passed, we need to guess
+    assert all(os.path.isabs(f) for f in filenames)
+    dirs = sorted(set([os.path.dirname(f) for f in filenames]))
+
+    # We need commonpath (3.5+), otherwise give up
+    if not hasattr(os.path, "commonpath"):
+        return dirs
+
+    common = os.path.commonpath(dirs)
+    # If the only common path is the root directory give up
+    if os.path.dirname(common) == common:
+        return dirs
+
+    return [common]
+
+
 def scanner_main(args):
     parser = _get_option_parser()
     (options, args) = parser.parse_args(args)
@@ -579,9 +600,9 @@ def scanner_main(args):
 
     transformer.namespace.c_includes = options.c_includes
     transformer.namespace.exported_packages = exported_packages
-    if not options.sources_top_dirs:
-        options.sources_top_dirs = [os.path.commonprefix(filenames).rpartition(os.path.sep)[0]]
-    writer = Writer(transformer.namespace, options.sources_top_dirs)
+
+    sources_top_dirs = get_source_root_dirs(options, filenames)
+    writer = Writer(transformer.namespace, sources_top_dirs)
     data = writer.get_encoded_xml()
 
     write_output(data, options)