[errors] Add location info to Oil language var references.

- And egg expression splices.
- Also update docs about read --line --with-eol.

doc/oil-help.md

@@ -402,10 +402,11 @@ The `.cell` action starts with `.` to indicate that its format is unstable.
 
 #### oil-read
 
-    read --line        # default var is $_line
-    read --line --qsn  # decode QSN too
-    read --all         # whole file including newline; var is $_all
-		read -0            # read until NUL, synonym for read -r -d ''
+    read --line             # default var is $_line
+    read --line --with-eol  # keep the \n
+    read --line --qsn       # decode QSN too
+    read --all              # whole file including newline; var is $_all
+    read -0                 # read until NUL, synonym for read -r -d ''
 
 #### run
 

doc/osh-help.md

@@ -556,6 +556,10 @@ Read a line from stdin, split it into tokens with the `$IFS` algorithm,
 and assign the tokens to the given variables.  When no VARs are given,
 assign to `$REPLY`.
 
+Note: When writing Oil, prefer the extensions documented in
+[oil-read]($oil-help).  The `read` builtin is confusing because `-r` needs to
+be explicitly enabled.
+
 Flags:
 
     -a ARRAY  assign the tokens to elements of this array

oil_lang/expr_eval.py

@@ -12,6 +12,7 @@
 from _devbuild.gen.runtime_asdl import (
     lvalue, value, value_e, scope_e,
 )
+from asdl import runtime
 from core.pyerror import e_die, log
 from frontend import consts
 from oil_lang import objects
@@ -65,14 +66,14 @@ def CheckCircularDeps(self):
     assert self.shell_ex is not None
     assert self.word_ev is not None
 
-  def LookupVar(self, var_name):
+  def LookupVar(self, var_name, span_id=runtime.NO_SPID):
     """Convert to a Python object so we can calculate on it natively."""
 
     # Lookup WITHOUT dynamic scope.
     val = self.mem.GetValue(var_name, which_scopes=scope_e.LocalOrGlobal)
     if val.tag == value_e.Undef:
       # TODO: Location info
-      e_die('Undefined variable %r', var_name)
+      e_die('Undefined variable %r', var_name, span_id=span_id)
 
     if val.tag == value_e.Str:
       return val.s
@@ -226,7 +227,7 @@ def EvalExpr(self, node):
       raise AssertionError(id_)
 
     if node.tag == expr_e.Var:
-      return self.LookupVar(node.name.val)
+      return self.LookupVar(node.name.val, span_id=node.name.span_id)
 
     if node.tag == expr_e.CommandSub:
       id_ = node.left_token.id
@@ -631,7 +632,7 @@ def _MaybeReplaceLeaf(self, node):
       new_leaf = re.LiteralChars(s, node.token.span_id)
 
     elif node.tag == re_e.Splice:
-      obj = self.LookupVar(node.name.val)
+      obj = self.LookupVar(node.name.val, span_id=node.name.span_id)
       if not isinstance(obj, objects.Regex):
         e_die("Can't splice object of type %r into regex", obj.__class__,
               token=node.name)

spec/oil-user-feedback.test.sh

@@ -92,15 +92,17 @@ foo
 baz
 ## END
 
-#### Location info undefined var in expression mode
+#### readonly in loop: explains why const doesn't work
 
-# TODO: Move this to runtime-errors?
+# TODO: Might want to change const in Oil...
+# bash actually prevents assignment and prints a warning, DOH.
 
-if (x) {
-  echo x
-}
+seq 3 | while read -r line; do
+  readonly stripped=${line//1/x}
+  #declare stripped=${line//1/x}
+  echo $stripped
+done
 ## status: 1
 ## STDOUT:
 x
 ## END
-

test/oil-runtime-errors.sh

@@ -7,6 +7,18 @@
 
 source test/common.sh
 
+OIL=${OIL:-bin/oil}
+
+_error-case() {
+  $OIL -c "$@"
+
+  # NOTE: This works with osh, not others.
+  local status=$?
+  if test $status != 1; then
+    die "Expected status 1, got $status"
+  fi
+}
+
 regex_literals() {
   var sq = / 'foo'+ /
   var dq = / "foo"+ /
@@ -25,6 +37,17 @@ regex_literals() {
   echo $bvs
 }
 
+undefined_vars() {
+  set +o errexit
+
+  _error-case 'echo hi; y = 2 + x + 3'
+  _error-case 'if (x) { echo hello }'
+  _error-case 'if ($x) { echo hi }'
+  _error-case 'if (${x}) { echo hi }'
+
+  _error-case 'x = / @yo /'
+}
+
 _run-test() {
   local name=$1
 
@@ -37,6 +60,7 @@ _run-test() {
 
 run-all-with-osh() {
   _run-test regex_literals
+  _run-test undefined_vars
 
   return 0  # success
 }