[translation] ctx_Alias

Hm this doesn't fix the infinite loop in case #3 of spec/alias?  Still
need to work on that.

mylib: add comments and test cases

frontend/parse_lib.py

@@ -62,7 +62,7 @@ def __init__(self):
     self.tokens = []  # type: List[Token]
 
     self.alias_words = []  # type: List[compound_word]  # words INSIDE an alias expansion
-    self.expanding_alias = False
+    self._expanding_alias = False
 
   def Clear(self):
     # type: () -> None
@@ -120,6 +120,36 @@ class _NullTrail(_BaseTrail):
   pass
 
 
+class ctx_Alias(object):
+  """Used by CommandParser so we know to be ready for FIRST alias word.
+
+  For example, for
+
+  alias ll='ls -l'
+
+  Then we want to capture 'ls' as the first word.
+
+  We do NOT want SetLatestWords or AppendToken to be active, because we don't
+  need other tokens from 'ls -l'.
+  
+  It would also probably cause bugs in history expansion, e.g. echo !1 should
+  be the first word the user typed, not the first word after alias expansion.
+  """
+
+  def __init__(self, trail):
+    # type: (_BaseTrail) -> None
+    trail._expanding_alias = True
+    self.trail = trail
+
+  def __enter__(self):
+    # type: () -> None
+    pass
+
+  def __exit__(self, type, value, traceback):
+    # type: (Any, Any, Any) -> None
+    self.trail._expanding_alias = False
+
+
 class Trail(_BaseTrail):
   """Info left by the parser to help us complete shell syntax and commands.
 
@@ -135,41 +165,18 @@ def Clear(self):
 
   def SetLatestWords(self, words, redirects):
     # type: (List[compound_word], List[redir]) -> None
-    if self.expanding_alias:
+    if self._expanding_alias:
       self.alias_words = words  # Save these separately
       return
     self.words = words
     self.redirects = redirects
 
   def AppendToken(self, token):
     # type: (Token) -> None
-    if self.expanding_alias:  # We don't want tokens inside aliases
+    if self._expanding_alias:  # We don't want tokens inside aliases
       return
     self.tokens.append(token)
 
-  def BeginAliasExpansion(self):
-    # type: () -> None
-    """Called by CommandParser so we know to be ready for FIRST alias word.
-
-    For example, for
-
-    alias ll='ls -l'
-
-    Then we want to capture 'ls' as the first word.
-
-    We do NOT want SetLatestWords or AppendToken to be active, because we don't
-    need other tokens from 'ls -l'.
-    
-    It would also probably cause bugs in history expansion, e.g. echo !1 should
-    be the first word the user typed, not the first word after alias expansion.
-    """
-    self.expanding_alias = True
-
-  def EndAliasExpansion(self):
-    # type: () -> None
-    """Go back to the normal trail collection mode."""
-    self.expanding_alias = False
-
 
 if TYPE_CHECKING:
   AliasesInFlight = List[Tuple[str, int]]

mycpp/mylib.h

@@ -894,10 +894,10 @@ inline int ord(Str* s) {
 }
 
 // https://stackoverflow.com/questions/3919995/determining-sprintf-buffer-size-whats-the-standard/11092994#11092994
-// Note: Python 2.7's intobject.c has an erroneous +6
-
-// This is 13, but
-// len('-2147483648') is 11, which means we only need 12?
+// Notes:
+// - Python 2.7's intobject.c has an erroneous +6
+// - This is 13, but len('-2147483648') is 11, which means we only need 12?
+// - This formula is valid for octal(), because 2^(3 bits) = 8
 const int kIntBufSize = CHAR_BIT * sizeof(int) / 3 + 3;
 
 inline Str* str(int i) {

mycpp/mylib_test.cc

@@ -143,17 +143,22 @@ TEST test_str_funcs() {
 
   int_str = str(-(1 << 31) + 1);
   log("i = %s", int_str->data_);
-  int_str = str(-(1 << 31));
+
+  int int_min = -(1 << 31);
+  int_str = str(int_min);
   log("i = %s", int_str->data_);
 
   int_str = mylib::hex_lower(15);
   ASSERT(str_equals0("f", int_str));
+  print(mylib::hex_lower(int_min));  // ASAN implicitly checks this
 
   int_str = mylib::hex_upper(15);
   ASSERT(str_equals0("F", int_str));
+  print(mylib::hex_upper(int_min));  // ASAN
 
   int_str = mylib::octal(15);
   ASSERT(str_equals0("17", int_str));
+  print(mylib::octal(int_min));  // ASAN
 
   Str* s1 = new Str("abc\0bcd", 7);
   ASSERT_EQ(7, len(s1));

osh/cmd_parse.py

@@ -728,22 +728,22 @@ def _MaybeExpandAliases(self, words):
     cp = self.parse_ctx.MakeOshParser(line_reader)
     cp.Init_AliasesInFlight(aliases_in_flight)
 
+    # break circular dep
+    from frontend import parse_lib
+
     # The interaction between COMPLETION and ALIASES requires special care.
     # See docstring of BeginAliasExpansion() in parse_lib.py.
     src = source.Alias(first_word_str, argv0_spid)
     with alloc.ctx_Location(self.arena, src):
-      trail = self.parse_ctx.trail
-      trail.BeginAliasExpansion()
-      try:
-        # _ParseCommandTerm() handles multiline commands, compound commands, etc.
-        # as opposed to ParseLogicalLine()
-        node = cp._ParseCommandTerm()
-      except error.Parse as e:
-        # Failure to parse alias expansion is a fatal error
-        # We don't need more handling here/
-        raise
-      finally:
-        trail.EndAliasExpansion()
+      with parse_lib.ctx_Alias(self.parse_ctx.trail):
+        try:
+          # _ParseCommandTerm() handles multiline commands, compound commands, etc.
+          # as opposed to ParseLogicalLine()
+          node = cp._ParseCommandTerm()
+        except error.Parse as e:
+          # Failure to parse alias expansion is a fatal error
+          # We don't need more handling here/
+          raise
 
     if 0:
       log('AFTER expansion:')