Validate inputs to ACE to prevent deadlocks.

Also, fix a bug that caused the "Malformed output from ACE" error to
be reported excessively.

Fixes #155

CHANGELOG.md

@@ -25,29 +25,34 @@
   hierarchy when looking for candidate nodes
 * `delphin.mrs.xmrs.Xmrs.from_xmrs()` and `delphin.mrs.eds.Eds.from_xmrs()`
   now take a `**kwargs` argument to facilitate the `convert` command (#160)
-* The following delphin.tdl functions are now private: `delphin.tdl._parse_avm()`,
-  `delphin.tdl._parse_affixes()`, `delphin.tdl._parse_typedef()`,
-  `delphin.tdl._parse_attr_val()`, `delphin.tdl._parse_cons_list()`,
-  `delphin.tdl._parse_conjunction()`, `delphin.tdl._parse_diff_list()` (#81)
+* The following `delphin.tdl` functions are now private:
+  `delphin.tdl._parse_avm()`, `delphin.tdl._parse_affixes()`,
+  `delphin.tdl._parse_typedef()`, `delphin.tdl._parse_attr_val()`,
+  `delphin.tdl._parse_cons_list()`, `delphin.tdl._parse_conjunction()`,
+  `delphin.tdl._parse_diff_list()` (#81)
 
 ### Fixed
 
 * Converting to PENMAN via the `convert` command should no longer crash for
   disconnected graphs, but print a log message to stderr, print a blank line
   to stdout, and then continue (#161)
 * Updated the docstrings for `delphin.mrs.xmrs.Xmrs.args()`,
-  `delphin.mrs.xmrs.Xmrs.outgoing_args()`, and `delphin.mrs.xmrs.Xmrs.incoming_args()`,
-  from "DMRS-style undirected links" to "MOD/EQ links" and updated the Return
-  value of `Xmrs.args()` and `Xmrs.outgoing_args` from `{nodeid: {}}` to
-  `{role: tgt}`(#133)
+  `delphin.mrs.xmrs.Xmrs.outgoing_args()`, and
+  `delphin.mrs.xmrs.Xmrs.incoming_args()`, from "DMRS-style undirected links"
+  to "MOD/EQ links" and updated the return value of `Xmrs.args()` and
+  `Xmrs.outgoing_args` from `{nodeid: {}}` to `{role: tgt}` (#133)
 * `delphin.mrs.compare.isomorphic()` compares predicates using a normalized form
 * Updated the code and the docstrings for references to 'string' and 'grammar'
   predicates to refer to 'surface' and 'abstract' predicates (#117)
-* `delphin.tdl.parse()` now accepts either a file or a filename as its argument (#104)
-* The following dump methods now allow either a file or filename as their arguments like
-  `delphin.mrs.penman.dump()`: `delphin.mrs.eds.dump()`, `delphin.mrs.simplemrs.dump()`, `delphin.mrs.simpledmrs.dump()`, `delphin.mrs.mrx.dump()`, `delphin.mrs.dmrx.dump()`,
+* `delphin.tdl.parse()` now accepts either a file or a filename argument (#104)
+* The following dump methods now allow either a file or filename as their
+  arguments like `delphin.mrs.penman.dump()`: `delphin.mrs.eds.dump()`,
+  `delphin.mrs.simplemrs.dump()`, `delphin.mrs.simpledmrs.dump()`,
+  `delphin.mrs.mrx.dump()`, `delphin.mrs.dmrx.dump()`,
   `delphin.mrs.prolog.dump()` (#152)
-
+* `delphin.interfaces.ace` now validates parser, transfer, and generator inputs
+  and refuses to process invalid inputs (#155)
+* `delphin.interfaces.ace` handles whitespace in s-expressions a bit better
 
 ### Deprecated
 

delphin/interfaces/ace.py

@@ -255,17 +255,28 @@ def interact(self, datum):
 
         This is the recommended method for sending and receiving data
         to/from an ACE process as it reduces the chances of
-        over-filling or reading past the end of the buffer. If input
-        item identifiers need to be tracked throughout processing, see
-        :meth:`process_item`.
+        over-filling or reading past the end of the buffer. It also
+        performs a simple validation of the input to help ensure that
+        one complete item is processed at a time.
+
+        If input item identifiers need to be tracked throughout
+        processing, see :meth:`process_item`.
 
         Args:
             datum (str): the input sentence or MRS
         Returns:
             :class:`~delphin.interfaces.ParseResponse`
         """
-        self.send(datum)
-        result = self.receive()
+        validated = self._validate_input(datum)
+        if validated:
+            self.send(validated)
+            result = self.receive()
+        else:
+            result, lines = _make_response(
+                [('NOTE: PyDelphin could not validate the input and '
+                  'refused to send it to ACE'),
+                 'SKIP: {}'.format(datum)],
+                self.run_info)
         result['input'] = datum
         return result
 
@@ -315,6 +326,11 @@ class AceParser(AceProcess):
     task = 'parse'
     _termini = [re.compile(r'^$'), re.compile(r'^$')]
 
+    def _validate_input(self, datum):
+        # valid input for parsing is non-empty
+        # (this relies on an empty string evaluating to False)
+        return datum.strip()
+
     def _default_receive(self):
         lines = self._result_lines()
         response, lines = _make_response(lines, self.run_info)
@@ -353,6 +369,9 @@ def __init__(self, grm, cmdargs=None, executable=None, env=None,
             tsdbinfo=False, **kwargs
         )
 
+    def _validate_input(self, datum):
+        return _possible_mrs(datum)
+
     def _default_receive(self):
         lines = self._result_lines()
         response, lines = _make_response(lines, self.run_info)
@@ -371,6 +390,9 @@ class AceGenerator(AceProcess):
     _cmdargs = ['-e', '--tsdb-notes']
     _termini = [re.compile(r'NOTE: tsdb parse: ')]
 
+    def _validate_input(self, datum):
+        return _possible_mrs(datum)
+
     def _default_receive(self):
         show_tree = '--show-realization-trees' in self.cmdargs
         show_mrs = '--show-realization-mrses' in self.cmdargs
@@ -544,6 +566,31 @@ def _ace_version(executable):
     return version
 
 
+def _possible_mrs(s):
+    start, end = -1, -1
+    depth = 0
+    for i, c in enumerate(s):
+        if c == '[':
+            if depth == 0:
+                start = i
+            depth += 1
+        elif c == ']':
+            depth -= 1
+            if depth == 0:
+                end = i + 1
+                break
+    # only valid if neither start nor end is -1
+    # note: this ignores any secondary MRSs on the same line
+    if start != -1 and end != -1:
+        # only log if taking a substring
+        if start != 0 and end != len(s):
+            logging.debug('Possible MRS found at <%d:%d>: %s', start, end, s)
+            s = s[start:end]
+        return s
+    else:
+        return False
+
+
 def _make_response(lines, run):
     response = ParseResponse({
         'NOTES': [],
@@ -575,7 +622,7 @@ def _sexpr_data(line):
         if len(expr.data) != 2:
             logging.error('Malformed output from ACE: {}'.format(line))
             break
-        line = expr.remainder
+        line = expr.remainder.lstrip()
         yield expr.data