Add length operator in variable expansions

corpus/expressions.txt

@@ -136,3 +136,21 @@ find "`dirname $file`" -name "$base"'*'
     (word)
     (string (simple_expansion (variable_name)))
     (raw_string)))
+
+=========================================
+Arrays and array expansions
+=========================================
+
+a=()
+b=(1 2 3)
+
+echo ${a[@]}
+echo ${#b[@]}
+
+---
+
+(program
+  (environment_variable_assignment (variable_name) (array))
+  (environment_variable_assignment (variable_name) (array (word) (word) (word)))
+  (command (command_name) (expansion (variable_name)))
+  (command (command_name) (expansion (variable_name))))

grammar.js

@@ -14,7 +14,8 @@ module.exports = grammar({
     $._heredoc_middle,
     $._heredoc_end,
     $.file_descriptor,
-    $._empty_value
+    $._empty_value,
+    '#'
   ],
 
   extras: $ => [
@@ -241,11 +242,15 @@ module.exports = grammar({
 
     expansion: $ => seq(
       '${',
+      choice(
+        $._variable_name,
+        seq('#', $._variable_name),
+        seq(
           $._variable_name,
-      optional(seq(
           choice(':', ':?', '=', ':-'),
           $._expression
-      )),
+        )
+      ),
       '}'
     ),
 

src/grammar.json

@@ -847,16 +847,33 @@
           "type": "STRING",
           "value": "${"
         },
+        {
+          "type": "CHOICE",
+          "members": [
             {
               "type": "SYMBOL",
               "name": "_variable_name"
             },
             {
-          "type": "CHOICE",
+              "type": "SEQ",
               "members": [
+                {
+                  "type": "STRING",
+                  "value": "#"
+                },
+                {
+                  "type": "SYMBOL",
+                  "name": "_variable_name"
+                }
+              ]
+            },
             {
               "type": "SEQ",
               "members": [
+                {
+                  "type": "SYMBOL",
+                  "name": "_variable_name"
+                },
                 {
                   "type": "CHOICE",
                   "members": [
@@ -883,9 +900,6 @@
                   "name": "_expression"
                 }
               ]
-            },
-            {
-              "type": "BLANK"
             }
           ]
         },
@@ -1111,6 +1125,10 @@
     {
       "type": "SYMBOL",
       "name": "_empty_value"
+    },
+    {
+      "type": "STRING",
+      "value": "#"
     }
   ],
   "inline": [

src/scanner.cc

@@ -13,6 +13,7 @@ enum TokenType {
   HEREDOC_END,
   FILE_DESCRIPTOR,
   EMPTY_VALUE,
+  LENGTH_OPERATOR
 };
 
 struct Scanner {
@@ -115,6 +116,16 @@ struct Scanner {
       }
     }
 
+    if (valid_symbols[LENGTH_OPERATOR]) {
+      if (lexer->lookahead == '#') {
+        advance(lexer);
+        if (iswalpha(lexer->lookahead)) {
+          lexer->result_symbol = LENGTH_OPERATOR;
+          return true;
+        }
+      }
+    }
+
     return false;
   }