[oil-language] Turn off bare assignment (parse_equals) by default

This addresses #937, which was also noted by a user.

Bare assignment like 'x = 42' was equivalent to 'const x = 42'.

However this causes inconsistency in programs.  We only want bare
assignment for config dialects like:

    server www.example.com {
      root = '/'
      port = 8080
    }

On the other hand we don't want

    proc p {
      const x = 42
      y = 43  # inconsistent
    }

Also add a failing test for bare assignment in blocks.  This is another
issue -- some blocks will introduce a new scope, and some won't.

So we don't want the static check for 'const already defined in scope'.
Instead bare assignment will only do DYNAMIC checks (similar to the top
level), and 'const' will do STATIC checks.

frontend/option_def.py

@@ -157,10 +157,11 @@ def DoneWithImplementedOptions(self):
 
 # Extra stuff that breaks too many programs.
 _AGGRESSIVE_PARSE_OPTIONS = [
-    ('parse_equals', False),   # x = 'var'
     ('parse_at_all', False),   # @ starting any word, e.g. @[] @{} @@ @_ @-
 
-    # Legacy syntax that is removed
+    # Legacy syntax that is removed.  These options are distinct from strict_*
+    # because they don't help you avoid bugs in bash programs.  They just makes
+    # the language more consistent.
     ('parse_backslash', True),
     ('parse_backticks', True),
     ('parse_dollar', True),
@@ -301,6 +302,9 @@ def _Init(opt_def):
   for name, default in _AGGRESSIVE_RUNTIME_OPTIONS:
     opt_def.Add(name, default=default, groups=['oil:all'])
 
+  # For configuration files.  bin/oven?
+  opt_def.Add('parse_equals')
+
   # Off by default.
   opt_def.Add('parse_tea')
 

osh/cmd_parse.py

@@ -1945,6 +1945,7 @@ def ParseCommand(self):
           # NOTE: tok.id should be Lit_Chars, but that check is redundant
           if (match.IsValidVarName(tok.val) and
               self.w_parser.LookPastSpace() == Id.Lit_Equals):
+            # bare declaration is equivalent to 'const'
             self.var_checker.Check(Id.KW_Const, tok)
 
             enode = self.w_parser.ParseBareDecl()

spec/oil-assign.test.sh

@@ -48,7 +48,7 @@ proc f {
 ## END
 
 #### top-level dynamic check: const can't be be mutated
-shopt -s oil:all
+shopt -s oil:all parse_equals
 
 x = 'foo'
 echo x=$x
@@ -215,7 +215,7 @@ write --sep ' ' @mylist
 ## END
 
 #### mixing assignment builtins and Oil assignment
-shopt -s oil:all
+shopt -s oil:all parse_equals
 
 proc local-var {
   local x=1
@@ -309,7 +309,11 @@ setvar L[0] = L
 ## END
 
 
-#### exit code of var, const, setvar
+#### exit code of var, const, setvar with command sub
+
+# NOTE: This feels PROBLEMATIC without command_sub_errexit feels like it should
+# be the last one ...
+
 var x = $(false)
 echo x=$x status=$?
 
@@ -322,5 +326,5 @@ echo y=$y status=$?
 ## STDOUT:
 x= status=1
 x=/42 status=1
-x=/43/44 status=1
+y=/43/44 status=1
 ## END

spec/oil-blocks.test.sh

@@ -295,3 +295,36 @@ command echo 2
 builtin echo 2
 pushd 2
 ## END
+
+#### Block with Bare Assignments
+
+# oil:all has parse_equals
+# is there any way to turn on parse_equals only in config blocks?
+# but we don't know what's a block ahead of time
+# I think we would have to check at runtime.  Look at VarChecker
+
+shopt --set oil:all
+
+proc rule(s, b Block) {
+  echo "rule $s"
+}
+
+proc myrules(name) { 
+  rule $name-python { 
+    kind = 'python'
+  }
+
+  rule $name-cc {
+    kind = 'cc'  # should NOT conflict
+  }
+}
+
+myrules foo
+myrules bar
+
+## STDOUT:
+rule foo-python
+rule foo-cc
+rule bar-ypthon
+rule bar-cc
+## END

spec/oil-keywords.test.sh

@@ -15,7 +15,7 @@ _ append(strs, 'c')
 write -- @strs
 
 # integer types too
-L = [5, 6]
+const L = [5, 6]
 _ append(L, 7)
 write -- @L
 

spec/oil-options.test.sh

@@ -503,21 +503,21 @@ k2
 ## END
 
 #### parse_equals: allows bare assignment
-shopt -s oil:all  # including nice options
+shopt -s parse_equals
 x = 1 + 2*3
 echo $x
 ## STDOUT:
 7
 ## END
 
 #### parse_equals: disallows ENV=val mycommand
-shopt -s oil:all
+shopt -s parse_equals
 ENV=val echo hi
 ## status: 2
 ## stdout-json: ""
 
 #### parse_equals: disallows var=val
-shopt -s oil:all
+shopt -s parse_equals
 var=val
 ## status: 2
 ## stdout-json: ""

spec/oil-regex.test.sh

@@ -636,7 +636,7 @@ echo $pat
 # octdigit     ::=  "0"..."7"
 # hexdigit     ::=  digit | "a"..."f" | "A"..."F"
 
-shopt -s oil:all
+shopt -s oil:all parse_equals  # Hm will need 'const'
 
 DecDigit = / [0-9] /
 BinDigit = / [0-1] /

test/spec.sh

@@ -889,7 +889,7 @@ oil-assign() {
 }
 
 oil-blocks() {
-  sh-spec spec/oil-blocks.test.sh --osh-failures-allowed 2 \
+  sh-spec spec/oil-blocks.test.sh --osh-failures-allowed 3 \
     $OSH_LIST "$@"
 }