allow each blocks to introduce reserved words as contexts (#222)

src/generators/Generator.js

@@ -58,7 +58,13 @@ export default class Generator {
 						// noop
 					}
 
-					else if ( contexts[ name ] ) {
+					else if ( name in contexts ) {
+						const context = contexts[ name ];
+						if ( context !== name ) {
+							// this is true for 'reserved' names like `root` and `component`
+							code.overwrite( node.start, node.start + name.length, context, true );
+						}
+
 						dependencies.push( ...contextDependencies[ name ] );
 						if ( !~usedContexts.indexOf( name ) ) usedContexts.push( name );
 					}

src/generators/dom/index.js

@@ -180,7 +180,7 @@ export default function dom ( parsed, source, options, names ) {
 		contexts: {},
 		indexes: {},
 
-		params: 'root',
+		params: [ 'root' ],
 		indexNames: {},
 		listNames: {},
 

src/generators/dom/visitors/EachBlock.js

@@ -2,6 +2,11 @@ import CodeBuilder from '../../../utils/CodeBuilder.js';
 import deindent from '../../../utils/deindent.js';
 import getBuilders from '../utils/getBuilders.js';
 
+const reserved = {
+	component: true,
+	root: true
+};
+
 export default {
 	enter ( generator, node ) {
 		const name = generator.getUniqueName( `eachBlock` );
@@ -172,16 +177,24 @@ export default {
 		const listNames = Object.assign( {}, generator.current.listNames );
 		listNames[ node.context ] = listName;
 
+		// ensure that contexts like `root` or `component` don't blow up the whole show
+		let context = node.context;
+		let c = 1;
+
+		while ( context in reserved || ~generator.current.params.indexOf( context ) ) {
+			context = `${node.context}$${c++}`;
+		}
+
 		const contexts = Object.assign( {}, generator.current.contexts );
-		contexts[ node.context ] = true;
+		contexts[ node.context ] = context;
 
 		const indexes = Object.assign( {}, generator.current.indexes );
 		if ( node.index ) indexes[ indexName ] = node.context;
 
 		const contextDependencies = Object.assign( {}, generator.current.contextDependencies );
 		contextDependencies[ node.context ] = dependencies;
 
-		const blockParams = generator.current.params + `, ${listName}, ${node.context}, ${indexName}`;
+		const blockParams = generator.current.params.concat( listName, context, indexName );
 
 		generator.push({
 			name: renderer,

src/generators/server-side-rendering/visitors/EachBlock.js

@@ -8,7 +8,7 @@ export default {
 		// TODO should this be the generator's job? It's duplicated between
 		// here and the equivalent DOM compiler visitor
 		const contexts = Object.assign( {}, generator.current.contexts );
-		contexts[ node.context ] = true;
+		contexts[ node.context ] = node.context;
 
 		const indexes = Object.assign( {}, generator.current.indexes );
 		if ( node.index ) indexes[ node.index ] = node.context;