Initial

resources/app/node_modules/peggy/lib/compiler/passes/remove-proxy-rules.js

@@ -0,0 +1,49 @@
+"use strict";
+
+const asts = require("../asts");
+const visitor = require("../visitor");
+
+// Removes proxy rules -- that is, rules that only delegate to other rule.
+function removeProxyRules(ast, options, session) {
+  function isProxyRule(node) {
+    return node.type === "rule" && node.expression.type === "rule_ref";
+  }
+
+  function replaceRuleRefs(ast, from, to) {
+    const replace = visitor.build({
+      rule_ref(node) {
+        if (node.name === from) {
+          node.name = to;
+
+          session.info(
+            `Proxy rule "${from}" replaced by the rule "${to}"`,
+            node.location,
+            [{
+              message: "This rule will be used",
+              location: asts.findRule(ast, to).nameLocation,
+            }]
+          );
+        }
+      },
+    });
+
+    replace(ast);
+  }
+
+  const indices = [];
+
+  ast.rules.forEach((rule, i) => {
+    if (isProxyRule(rule)) {
+      replaceRuleRefs(ast, rule.name, rule.expression.name);
+      if (options.allowedStartRules.indexOf(rule.name) === -1) {
+        indices.push(i);
+      }
+    }
+  });
+
+  indices.reverse();
+
+  indices.forEach(i => { ast.rules.splice(i, 1); });
+}
+
+module.exports = removeProxyRules;