[eggex] _match() fails when arg is out of range

Also test that unmatched groups return null, not ''

builtin/func_eggex.py

@@ -5,6 +5,7 @@
 from __future__ import print_function
 
 from _devbuild.gen.value_asdl import value, value_t
+from core import error
 from core import state
 from core import vm
 from frontend import typed_args
@@ -24,17 +25,25 @@ def __init__(self, mem):
 
     def Call(self, rd):
         # type: (typed_args.Reader) -> value_t
-        n = rd.OptionalInt(default_=0)
 
-        # TODO: Support strings
-        s = self.mem.GetMatch(n)
-        # YSH code doesn't deal well with exceptions!
-        #if s is None:
-        #  raise IndexError('No such group')
-        if s is not None:
-            return value.Str(s)
-
-        return value.Null
+        # TODO: Support strings for named captures
+        i = rd.OptionalInt(default_=0)
+
+        matches = self.mem.GetRegexMatches()
+        num_groups = len(matches)  # including group 0
+        if i < num_groups:
+            captured = matches[i]
+            if captured is None:
+                return value.Null
+            else:
+                return value.Str(captured)
+        else:
+            if num_groups == 0:
+                msg = 'No regex capture groups'
+            else:
+                msg = 'Expected capture group less than %d, got %d' % (
+                    num_groups, i)
+            raise error.UserError(2, msg, rd.LeftParenToken())
 
 
 class Start(vm._Callable):

core/process.py

@@ -1681,7 +1681,8 @@ def GetJobWithSpec(self, job_spec):
 
         # TODO: Add support for job specs based on prefixes of process argv.
         m = util.simple_regex_search(r'^%([0-9]+)$', job_spec)
-        if m is not None and len(m) > 1:
+        if m is not None:
+            assert len(m) == 2
             job_id = int(m[1])
             if job_id in self.jobs:
                 return self.jobs[job_id]

core/state.py

@@ -2152,13 +2152,9 @@ def SetMatches(self, matches):
         # type: (List[str]) -> None
         self.regex_matches[-1] = matches
 
-    def GetMatch(self, i):
-        # type: (int) -> Optional[str]
-        top = self.regex_matches[-1]
-        if i < len(top):
-            return top[i]
-        else:
-            return None
+    def GetRegexMatches(self):
+        # type: () -> List[Optional[str]]
+        return self.regex_matches[-1]
 
 
 #

spec/ysh-regex.test.sh

@@ -131,18 +131,38 @@ if (s ~ '[[:digit:]]+') {
 }
 # Should be cleared now
 # should this be Undef rather than ''?
-var x = _match(0)
-var y = _match(1)
-if (x === null and y === null) {
-  echo 'cleared'
+try {
+  var x = _match(0)
+}
+if (_status === 2) {
+  echo 'got expected status 2'
+}
+
+try {
+  var y = _match(1)
+}
+if (_status === 2) {
+  echo 'got expected status 2'
 }
 
 ## STDOUT:
 matches
 ['foo', 'oo']
 does not match
 ['foo', 'oo']
-cleared
+got expected status 2
+got expected status 2
+## END
+
+#### _match() returns null when group doesn't match
+shopt -s ysh:upgrade
+
+var pat = / <capture 'a'> | <capture 'b'> /
+if ('b' ~ pat) {
+  echo "$[_match(1)] $[_match(2)]"
+}
+## STDOUT:
+null b
 ## END
 
 #### _start() and _end()