# HG changeset patch
# User Anton Shestakov <av6@dwimlabs.net>
# Date 2018-12-13 09:18:57
# Node ID e54bfde922f20c840a67fcb3ac00ec338d4c4d29
# Parent  fcdff048a8e5ffdcaacab179c489f581853f4629

revset: move subscript relation functions to its own dict

This will help adding more relation functions in extensions.

We skip short names (that consist of one letter) while raising
UnknownIdentifier because such names cannot be suggested anyway: the similarity
cutoff in dispatch._getsimilar() is currently 0.6.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -218,6 +218,15 @@ def notset(repo, subset, x, order):
 def relationset(repo, subset, x, y, order):
     raise error.ParseError(_("can't use a relation in this context"))
 
+def generationsrel(repo, subset, x, rel, n, order):
+    # TODO: support range, rewrite tests, and drop startdepth argument
+    # from ancestors() and descendants() predicates
+    if n <= 0:
+        n = -n
+        return _ancestors(repo, subset, x, startdepth=n, stopdepth=n + 1)
+    else:
+        return _descendants(repo, subset, x, startdepth=n, stopdepth=n + 1)
+
 def relsubscriptset(repo, subset, x, y, z, order):
     # this is pretty basic implementation of 'x#y[z]' operator, still
     # experimental so undocumented. see the wiki for further ideas.
@@ -225,17 +234,11 @@ def relsubscriptset(repo, subset, x, y, 
     rel = getsymbol(y)
     n = getinteger(z, _("relation subscript must be an integer"))
 
-    # TODO: perhaps this should be a table of relation functions
-    if rel in ('g', 'generations'):
-        # TODO: support range, rewrite tests, and drop startdepth argument
-        # from ancestors() and descendants() predicates
-        if n <= 0:
-            n = -n
-            return _ancestors(repo, subset, x, startdepth=n, stopdepth=n + 1)
-        else:
-            return _descendants(repo, subset, x, startdepth=n, stopdepth=n + 1)
+    if rel in subscriptrelations:
+        return subscriptrelations[rel](repo, subset, x, rel, n, order)
 
-    raise error.UnknownIdentifier(rel, ['generations'])
+    relnames = [r for r in subscriptrelations.keys() if len(r) > 1]
+    raise error.UnknownIdentifier(rel, relnames)
 
 def subscriptset(repo, subset, x, y, order):
     raise error.ParseError(_("can't use a subscript in this context"))
@@ -2215,6 +2218,11 @@ methods = {
     "parentpost": parentpost,
 }
 
+subscriptrelations = {
+    "g": generationsrel,
+    "generations": generationsrel,
+}
+
 def lookupfn(repo):
     return lambda symbol: scmutil.isrevsymbol(repo, symbol)
 
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -649,6 +649,17 @@ parse errors of relation, subscript and 
   hg: parse error: relation subscript must be an integer
   [255]
 
+suggested relations
+
+  $ hg debugrevspec '.#generafions[0]'
+  hg: parse error: unknown identifier: generafions
+  (did you mean generations?)
+  [255]
+
+  $ hg debugrevspec '.#f[0]'
+  hg: parse error: unknown identifier: f
+  [255]
+
 parsed tree at stages:
 
   $ hg debugrevspec -p all '()'