[prompt, test, cleanup] Add a cache for the prompt tokens.

Also:

- Add a real-world demo/test for $PS1 (that still needs work.)
- Add a cache for the prompt tokens
- Rename to prompt.test.sh.
- [spec/loop] Make the test case a bit harder.

core/ui.py

@@ -164,13 +164,17 @@ def __init__(self, arena, parse_ctx, ex):
     self.hostname = None
     self.username = None
 
-    self.cache = _PromptCache()
-    self.parse_cache = {}  # PS1 value -> CompoundWord.
+    self.cache = _PromptCache()  # Cache to save syscalls / libc calls.
 
-  def _ReplaceBackslashCodes(self, s):
+    # These caches should reduce memory pressure a bit.  We don't want to
+    # reparse the prompt twice every time you hit enter.
+    self.tokens_cache = {}  # string -> list of tokens
+    self.parse_cache = {}  # string -> CompoundWord.
+
+  def _ReplaceBackslashCodes(self, tokens):
     ret = []
     non_printing = 0
-    for id_, value in match.PS1_LEXER.Tokens(s):
+    for id_, value in tokens:
       # BadBacklash means they should have escaped with \\, but we can't 
       # make this an error.
       if id_ in (Id.PS_Literals, Id.PS_BadBackslash):
@@ -218,37 +222,42 @@ def _ReplaceBackslashCodes(self, s):
 
     return ''.join(ret)
 
-  def PS1(self):
-    val = self.ex.mem.GetVar('PS1')
-    return self.EvalPS1(val)
-
-  def EvalPS1(self, val):
+  def EvalPrompt(self, val):
+    """Perform the two evaluations that bash does.  Used by $PS1 and ${x@P}."""
     if val.tag != value_e.Str:
-      return DEFAULT_PS1
+      return DEFAULT_PS1  # no evaluation necessary
+
+    try:
+      tokens = self.tokens_cache[val.s]
+    except KeyError:
+      tokens = match.PS1_LEXER.Tokens(val.s)
+      self.tokens_cache[val.s] = tokens
 
     # First replacements.  TODO: Should we cache this too?
-    ps1_str = self._ReplaceBackslashCodes(val.s)
+    ps1_str = self._ReplaceBackslashCodes(tokens)
 
     # The prompt is often constant, so we can avoid parsing it.
     # NOTE: This is copied from the PS4 logic in Tracer.
     try:
       ps1_word = self.parse_cache[ps1_str]
     except KeyError:
       w_parser = self.parse_ctx.MakeWordParserForPlugin(ps1_str, self.arena)
-
       try:
         ps1_word = w_parser.ReadPS()
       except Exception as e:
         error_str = '<ERROR: cannot parse PS1>'
         t = ast.token(Id.Lit_Chars, error_str, const.NO_INTEGER)
         ps1_word = ast.CompoundWord([ast.LiteralPart(t)])
-
-    self.parse_cache[ps1_str] = ps1_word
+      self.parse_cache[ps1_str] = ps1_word
 
     # e.g. "${debian_chroot}\u" -> '\u'
     val2 = self.ex.word_ev.EvalWordToString(ps1_word)
     return val2.s
 
+  def PS1(self):
+    val = self.ex.mem.GetVar('PS1')
+    return self.EvalPrompt(val)
+
 
 def PrintFilenameAndLine(span_id, arena, f=sys.stderr):
   line_span = arena.GetLineSpan(span_id)

core/word_eval.py

@@ -563,7 +563,7 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
         if op.op_id == Id.VOp0_P:
           # TODO: Use dependency injection
           #val = self.prompt._EvalPS1(val)
-          prompt = ui.PROMPT.EvalPS1(val)
+          prompt = ui.PROMPT.EvalPrompt(val)
           val = runtime.Str(prompt)
         else:
           raise NotImplementedError(op.op_id)

demo/git-prompt.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+#
+# Copied from my bashrc.
+
+# TODO: The branch name isn't being displayed?
+git-prompt() {
+  . testdata/completion/git
+  . ~/git-prompt.sh
+
+  export PS1='\u@\h \w$(__git_ps1 " (%s)")\$ '
+}
+
+git-prompt
+

spec/loop.test.sh

@@ -129,19 +129,26 @@ one
 
 #### continue in subshell
 for i in $(seq 3); do
-  echo $i
+  echo "> $i"
   ( if true; then continue; fi; echo "Should not print" )
+  echo ". $i"
 done
 ## STDOUT:
-1
-2
-3
+> 1
+. 1
+> 2
+. 2
+> 3
+. 3
 ## END
 ## BUG mksh STDOUT:
-1
+> 1
 Should not print
-2
+. 1
+> 2
 Should not print
-3
+. 2
+> 3
 Should not print
+. 3
 ## END

test/spec.sh

@@ -207,8 +207,8 @@ smoke() {
   sh-spec spec/smoke.test.sh ${REF_SHELLS[@]} $OSH_LIST "$@"
 }
 
-ps1-replacements() {
-  sh-spec spec/ps1-replacements.test.sh --osh-failures-allowed 1 \
+prompt() {
+  sh-spec spec/prompt.test.sh --osh-failures-allowed 1 \
     $BASH $OSH_LIST "$@"
 }