extensions: peek command table of disabled extensions without importing
authorYuya Nishihara <yuya@tcha.org>
Thu, 03 May 2018 18:38:02 +0900
changeset 38195 bdf344aea0ee
parent 38194 aa10675c5dd6
child 38196 b39958d6b81b
extensions: peek command table of disabled extensions without importing With chg where demandimport disabled, and if disk cache not warm, it took more than 5 seconds to get "unknown command" error when you typo a command name. This is horrible UX. The new implementation is less accurate than the original one as Python can do anything at import time and cmdtable may be imported from another module, but I think it's good enough. Note that the new implementation has to parse .py files, which is slightly slower than executing .pyc if demandimport is enabled.
mercurial/extensions.py
tests/test-extension.t
--- a/mercurial/extensions.py	Thu Apr 26 23:00:19 2018 -0400
+++ b/mercurial/extensions.py	Thu May 03 18:38:02 2018 +0900
@@ -7,6 +7,8 @@
 
 from __future__ import absolute_import
 
+import ast
+import collections
 import functools
 import imp
 import inspect
@@ -655,34 +657,67 @@
     if name in paths:
         return _disabledhelp(paths[name])
 
+def _walkcommand(node):
+    """Scan @command() decorators in the tree starting at node"""
+    todo = collections.deque([node])
+    while todo:
+        node = todo.popleft()
+        if not isinstance(node, ast.FunctionDef):
+            todo.extend(ast.iter_child_nodes(node))
+            continue
+        for d in node.decorator_list:
+            if not isinstance(d, ast.Call):
+                continue
+            if not isinstance(d.func, ast.Name):
+                continue
+            if d.func.id != r'command':
+                continue
+            yield d
+
+def _disabledcmdtable(path):
+    """Construct a dummy command table without loading the extension module
+
+    This may raise IOError or SyntaxError.
+    """
+    with open(path, 'rb') as src:
+        root = ast.parse(src.read(), path)
+    cmdtable = {}
+    for node in _walkcommand(root):
+        if not node.args:
+            continue
+        a = node.args[0]
+        if isinstance(a, ast.Str):
+            name = pycompat.sysbytes(a.s)
+        elif pycompat.ispy3 and isinstance(a, ast.Bytes):
+            name = a.s
+        else:
+            continue
+        cmdtable[name] = (None, [], b'')
+    return cmdtable
+
 def _finddisabledcmd(ui, cmd, name, path, strict):
     try:
-        mod = loadpath(path, 'hgext.%s' % name)
-    except Exception:
+        cmdtable = _disabledcmdtable(path)
+    except (IOError, SyntaxError):
         return
     try:
-        aliases, entry = cmdutil.findcmd(cmd,
-            getattr(mod, 'cmdtable', {}), strict)
+        aliases, entry = cmdutil.findcmd(cmd, cmdtable, strict)
     except (error.AmbiguousCommand, error.UnknownCommand):
         return
-    except Exception:
-        ui.warn(_('warning: error finding commands in %s\n') % path)
-        ui.traceback()
-        return
     for c in aliases:
         if c.startswith(cmd):
             cmd = c
             break
     else:
         cmd = aliases[0]
-    doc = gettext(pycompat.getdoc(mod))
+    doc = _disabledhelp(path)
     return (cmd, name, doc)
 
 def disabledcmd(ui, cmd, strict=False):
-    '''import disabled extensions until cmd is found.
+    '''find cmd from disabled extensions without importing.
     returns (cmdname, extname, doc)'''
 
-    paths = _disabledpaths(strip_init=True)
+    paths = _disabledpaths()
     if not paths:
         raise error.UnknownCommand(cmd)
 
--- a/tests/test-extension.t	Thu Apr 26 23:00:19 2018 -0400
+++ b/tests/test-extension.t	Thu May 03 18:38:02 2018 +0900
@@ -1229,9 +1229,14 @@
 
   $ cat > hgext/forest.py <<EOF
   > cmdtable = None
+  > @command()
+  > def f():
+  >     pass
+  > @command(123)
+  > def g():
+  >     pass
   > EOF
   $ hg --config extensions.path=./path.py help foo > /dev/null
-  warning: error finding commands in $TESTTMP/hgext/forest.py
   abort: no such help topic: foo
   (try 'hg help --keyword foo')
   [255]