Change: docgen to not change output needlessly

If the output file wouldn't change, then don't update it.

This is imperfect, since it still needs to produce the output file,
so it can spend a bit of processing power to make no changes. But the
alternative would be to make needless changes.

1 files changed, 26 insertions, 0 deletions

diff --git a/subplot.py b/subplot.py
index bc972f8..48320b6 100644
--- a/subplot.py
+++ b/subplot.py
@@ -87,6 +87,32 @@ def stdout_matches(ctx, pattern):
     stdout = ctx.get('stdout', '')
     return pattern in stdout
 
+def _get_metadata(filename):
+    st = os.lstat(filename)
+    keys = [
+        'st_dev',
+        'st_gid',
+        'st_ino',
+        'st_mode',
+        'st_mtime',
+        'st_size',
+        'st_uid',
+    ]
+    return {
+        key: getattr(st, key)
+        for key in keys
+    }
+
+def remember_metadata(ctx, filename=None):
+    ctx['remembered-metadata'] = _get_metadata(filename)
+
+def has_same_metadata_as_remembered(ctx, filename=None):
+    assert_eq(ctx['remembered-metadata'], _get_metadata(filename))
+
+def only_these_files_exist(ctx, filenames=None):
+    filenames = filenames.replace(',', '').split()
+    assert_eq(set(os.listdir('.')), set(filenames))
+
 def runcmd(ctx, argv):
     p = subprocess.Popen(argv, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     stdout, stderr = p.communicate("")