revset: reduce nesting of chained 'or' operations (issue4624)

This reduces the stack depth of chained 'or' operations:
 - from O(n) to O(1) at the parsing, alias expansion and optimization phases
 - from O(n) to O(log(n)) at the evaluation phase

simplifyinfixops() must be applied immediately after the parsing phase.
Otherwise, alias expansion would crash by "maximum recursion depth exceeded"
error.

Test cases use 'x:y|y:z' instead of 'x|y' because I'm planning to optimize
'x|y' in a different way.

Benchmarks:

0) 605b1d32c1c0
1) this patch

revset  #0: 0 + 1 + 2 + ... + 200
0) wall 0.026347 comb 0.030000 user 0.030000 sys 0.000000 (best of 101)
1) wall 0.023858 comb 0.030000 user 0.030000 sys 0.000000 (best of 112)

revset  #1: 0 + 1 + 2 + ... + 1000
0) maximum recursion depth exceeded
1) wall 0.483341 comb 0.480000 user 0.480000 sys 0.000000 (best of 20)

revset  #2: sort(0 + 1 + 2 + ... + 200)
0) wall 0.013404 comb 0.010000 user 0.010000 sys 0.000000 (best of 196)
1) wall 0.006814 comb 0.010000 user 0.010000 sys 0.000000 (best of 375)

revset  #3: sort(0 + 1 + 2 + ... + 1000)
0) maximum recursion depth exceeded
1) wall 0.035240 comb 0.040000 user 0.040000 sys 0.000000 (best of 100)

mercurial/revset.py

@@ -356,10 +356,9 b' def dagrange(repo, subset, x, y):'
 def andset(repo, subset, x, y):
     return getset(repo, getset(repo, subset, x), y)
 
-def orset(repo, subset, x, y):
-    xl = getset(repo, subset, x)
-    yl = getset(repo, subset, y)
-    return xl + yl
+def orset(repo, subset, *xs):
+    rs = [getset(repo, subset, x) for x in xs]
+    return _combinesets(rs)
 
 def notset(repo, subset, x):
     return subset - getset(repo, subset, x)
@@ -2160,13 +2159,11 b' def optimize(x, small):'
             return w, (op, tb, ta)
         return w, (op, ta, tb)
     elif op == 'or':
-        wa, ta = optimize(x[1], False)
-        wb, tb = optimize(x[2], False)
+        ws, ts = zip(*[optimize(y, False) for y in x[1:]])
         # we can't reorder trees by weight because it would change the order.
         # ("sort(a + b)" == "sort(b + a)", but "a + b" != "b + a")
-        #   if wb < wa:
-        #       tb, ta = ta, tb
-        return max(wa, wb), (op, ta, tb)
+        #   ts = tuple(t for w, t in sorted(zip(ws, ts), key=lambda wt: wt[0]))
+        return max(ws), (op,) + ts
     elif op == 'not':
         # Optimize not public() to _notpublic() because we have a fast version
         if x[1] == ('func', ('symbol', 'public'), None):
@@ -2384,7 +2381,7 b' def _parsealiasdefn(defn, args):'
     tree, pos = p.parse(defn)
     if pos != len(defn):
         raise error.ParseError(_('invalid token'), pos)
-    return tree
+    return parser.simplifyinfixops(tree, ('or',))
 
 class revsetalias(object):
     # whether own `error` information is already shown or not.
@@ -2515,7 +2512,7 b' def parse(spec, lookup=None):'
     tree, pos = p.parse(spec, lookup=lookup)
     if pos != len(spec):
         raise error.ParseError(_("invalid token"), pos)
-    return tree
+    return parser.simplifyinfixops(tree, ('or',))
 
 def posttreebuilthook(tree, repo):
     # hook for extensions to execute code on the optimized tree

tests/test-glog.t

@@ -1469,13 +1469,12 b' glog always reorders nodes which explain'
   (group
     (group
       (or
-        (or
-          (func
-            ('symbol', 'branch')
-            ('string', 'default'))
-          (func
-            ('symbol', 'branch')
-            ('string', 'branch')))
+        (func
+          ('symbol', 'branch')
+          ('string', 'default'))
+        (func
+          ('symbol', 'branch')
+          ('string', 'branch'))
         (func
           ('symbol', 'branch')
           ('string', 'branch')))))

tests/test-revset.t

@@ -128,16 +128,15 b' trivial'
   6
   $ try '0|1|2'
   (or
-    (or
-      ('symbol', '0')
-      ('symbol', '1'))
+    ('symbol', '0')
+    ('symbol', '1')
     ('symbol', '2'))
   * set:
   <addset
+    <baseset [0]>,
     <addset
-      <baseset [0]>,
-      <baseset [1]>>,
-    <baseset [2]>>
+      <baseset [1]>,
+      <baseset [2]>>>
   0
   1
   2
@@ -910,6 +909,49 b' test that `or` operation skips duplicate'
   4
   5
 
+test that chained `or` operations make balanced addsets
+
+  $ try '0:1|1:2|2:3|3:4|4:5'
+  (or
+    (range
+      ('symbol', '0')
+      ('symbol', '1'))
+    (range
+      ('symbol', '1')
+      ('symbol', '2'))
+    (range
+      ('symbol', '2')
+      ('symbol', '3'))
+    (range
+      ('symbol', '3')
+      ('symbol', '4'))
+    (range
+      ('symbol', '4')
+      ('symbol', '5')))
+  * set:
+  <addset
+    <addset
+      <spanset+ 0:1>,
+      <spanset+ 1:2>>,
+    <addset
+      <spanset+ 2:3>,
+      <addset
+        <spanset+ 3:4>,
+        <spanset+ 4:5>>>>
+  0
+  1
+  2
+  3
+  4
+  5
+
+test that chained `or` operations never eat up stack (issue4624)
+(uses `0:1` instead of `0` to avoid future optimization of trivial revisions)
+
+  $ hg log -T '{rev}\n' -r "`python -c "print '|'.join(['0:1'] * 500)"`"
+  0
+  1
+
 check that conversion to only works
   $ try --optimize '::3 - ::1'
   (minus
@@ -1352,6 +1394,44 b' test nesting and variable passing'
   <baseset [5]>
   5
 
+test chained `or` operations are flattened at parsing phase
+
+  $ echo 'chainedorops($1, $2, $3) = $1|$2|$3' >> .hg/hgrc
+  $ try 'chainedorops(0:1, 1:2, 2:3)'
+  (func
+    ('symbol', 'chainedorops')
+    (list
+      (list
+        (range
+          ('symbol', '0')
+          ('symbol', '1'))
+        (range
+          ('symbol', '1')
+          ('symbol', '2')))
+      (range
+        ('symbol', '2')
+        ('symbol', '3'))))
+  (or
+    (range
+      ('symbol', '0')
+      ('symbol', '1'))
+    (range
+      ('symbol', '1')
+      ('symbol', '2'))
+    (range
+      ('symbol', '2')
+      ('symbol', '3')))
+  * set:
+  <addset
+    <spanset+ 0:1>,
+    <addset
+      <spanset+ 1:2>,
+      <spanset+ 2:3>>>
+  0
+  1
+  2
+  3
+
 test variable isolation, variable placeholders are rewritten as string
 then parsed and matched again as string. Check they do not leak too
 far away.