From 851d8edfddc6a4a74de472721c67579882ced34b Mon Sep 17 00:00:00 2001
From: Futago-za Ryuu <futagoza.ryuu@gmail.com>
Date: Wed, 31 Jan 2018 02:04:19 +0000
Subject: [PATCH] Implement warning emitter (Closes #327)

---
 lib/compiler/session.js                   |  4 ++
 test/spec/unit/compiler/passes/helpers.js | 76 ++++++++++++++++++-----
 2 files changed, 66 insertions(+), 14 deletions(-)

diff --git a/lib/compiler/session.js b/lib/compiler/session.js
index a33ac13..7322356 100644
--- a/lib/compiler/session.js
+++ b/lib/compiler/session.js
@@ -16,6 +16,8 @@ class Session {
         this.passes = options.passes || [];
         this.visitor = options.visitor || ast.visitor;
 
+        if ( typeof options.warn === "function" ) this.warn = options.warn;
+
     }
 
     parse( input, options ) {
@@ -30,6 +32,8 @@ class Session {
 
     }
 
+    warn( message, details ) {}
+
 }
 
 module.exports = Session;
diff --git a/test/spec/unit/compiler/passes/helpers.js b/test/spec/unit/compiler/passes/helpers.js
index 1cd5469..683f7c0 100644
--- a/test/spec/unit/compiler/passes/helpers.js
+++ b/test/spec/unit/compiler/passes/helpers.js
@@ -9,12 +9,8 @@ module.exports = function ( chai, utils ) {
 
     const Assertion = chai.Assertion;
 
-    Assertion.addMethod( "changeAST", function ( grammar, props, options, additionalRuleProps ) {
-
-        options = typeof options !== "undefined" ? options : {};
-        additionalRuleProps = typeof additionalRuleProps !== "undefined" ? additionalRuleProps : { reportFailures: true };
+    function parse( grammar, session, options ) {
 
-        const session = new Session( { grammar } );
         const ast = session.parse( grammar );
 
         if ( ! options.allowedStartRules ) {
@@ -25,6 +21,18 @@ module.exports = function ( chai, utils ) {
 
         }
 
+        return ast;
+
+    }
+
+    Assertion.addMethod( "changeAST", function ( grammar, props, options, additionalRuleProps ) {
+
+        options = typeof options !== "undefined" ? options : {};
+        additionalRuleProps = typeof additionalRuleProps !== "undefined" ? additionalRuleProps : { reportFailures: true };
+
+        const session = new Session( { grammar } );
+        const ast = parse( grammar, session, options );
+
         ast.rules = ast.rules.map( rule => Object.assign( rule, additionalRuleProps ) );
 
         utils.flag( this, "object" )( ast, session, options );
@@ -38,15 +46,7 @@ module.exports = function ( chai, utils ) {
         options = typeof options !== "undefined" ? options : {};
 
         const session = new Session( { grammar } );
-        const ast = session.parse( grammar );
-
-        if ( ! options.allowedStartRules ) {
-
-            options.allowedStartRules = ast.rules.length > 0
-                ? [ ast.rules[ 0 ].name ]
-                : [];
-
-        }
+        const ast = parse( grammar, session, options );
 
         let passed, result;
 
@@ -84,4 +84,52 @@ module.exports = function ( chai, utils ) {
 
     } );
 
+    Assertion.addMethod( "reportWarning", function ( grammar, warnings, options ) {
+
+        warnings = Array.isArray( warnings )
+            ? warnings
+            : warnings == null
+                ? []
+                : [ warnings ];
+
+        options = typeof options !== "undefined" ? options : {};
+
+        const messages = [];
+        function warn( message ) {
+
+            messages.push( message );
+
+        }
+
+        const session = new Session( { grammar, warn } );
+        const ast = parse( grammar, session, options );
+
+        utils.flag( this, "object" )( ast, session, options );
+
+        const messagesCount = messages.length;
+        const warningsCount = warnings.length;
+
+        if ( warnings.length )
+
+            this.assert(
+                messagesCount === warningsCount,
+                `expected #{this} to report ${ warningsCount } warnings, but it reported ${ messagesCount } warnings`,
+                `expected #{this} to not report ${ warningsCount } warnings`,
+                warnings,
+                messages
+            );
+
+        warnings.forEach( warning => {
+
+            this.assert(
+                messages.indexOf( warning ) !== -1,
+                "expected #{this} to report the warning #{exp}, but it didn't",
+                "expected #{this} to not report the warning #{exp}",
+                warning
+            );
+
+        } );
+
+    } );
+
 };