Repository: sveltejs/svelte (JavaScript)
Date: 2018-03-13 16:34:56+00:00
Task type: Bug Fix

Issue:
Context variable overrides shared helper when `hydratable: true`
It seems having keys with the same name as shared helpers can cause problems in v1.57 SSR.

eg. This runs fine on the repl, but will error when SSRing because `claim` will try to call `children`:

https://svelte.technology/repl?version=1.57.0&gist=9a26ffaad3e8741640d51c55c1600ead

```js
// (1:0) {{#if children}}
function create_if_block(component, state) {
	var ul;

	var children = state.children;

	var each_blocks = [];

	for (var i = 0; i < children.length; i += 1) {
		each_blocks[i] = create_each_block(component, assign({}, state, {
			children: children,
			child: children[i],
			child_index: i
		}));
	}

	return {
		c: function create() {
			ul = createElement("ul");

			for (var i = 0; i < each_blocks.length; i += 1) {
				each_blocks[i].c();
			}
		},

		l: function claim(nodes) {
			ul = claimElement(nodes, "UL", {}, false);
			var ul_nodes = children(ul); // <- children is not a function

			for (var i = 0; i < each_blocks.length; i += 1) {
				each_blocks[i].l(ul_nodes);
			}

			ul_nodes.forEach(detachNode);
		},
```


Issue discussion:

Solution patch:
diff --git a/src/generators/dom/Block.ts b/src/generators/dom/Block.ts
--- a/src/generators/dom/Block.ts
+++ b/src/generators/dom/Block.ts
@@ -44,6 +44,7 @@ export default class Block {
 	listNames: Map<string, string>;
 	indexName: string;
 	listName: string;
+	listAlias: string;
 
 	builders: {
 		init: CodeBuilder;
@@ -120,6 +121,8 @@ export default class Block {
 			.set('state', this.getUniqueName('state'));
 		if (this.key) this.aliases.set('key', this.getUniqueName('key'));
 
+		this.listAlias = this.getUniqueName(this.listName);
+
 		this.hasUpdateMethod = false; // determined later
 	}
 
diff --git a/src/generators/nodes/EachBlock.ts b/src/generators/nodes/EachBlock.ts
--- a/src/generators/nodes/EachBlock.ts
+++ b/src/generators/nodes/EachBlock.ts
@@ -75,14 +75,14 @@ export default class EachBlock extends Node {
 		}
 
 		this.contextProps = [
-			`${this.block.listName}: ${this.block.listName}`,
-			`${this.context}: ${this.block.listName}[#i]`,
+			`${this.block.listName}: ${this.block.listAlias}`,
+			`${this.context}: ${this.block.listAlias}[#i]`,
 			`${this.block.indexName}: #i`
 		];
 
 		if (this.destructuredContexts) {
 			for (let i = 0; i < this.destructuredContexts.length; i += 1) {
-				this.contextProps.push(`${this.destructuredContexts[i]}: ${this.block.listName}[#i][${i}]`);
+				this.contextProps.push(`${this.destructuredContexts[i]}: ${this.block.listAlias}[#i][${i}]`);
 			}
 		}
 
@@ -117,7 +117,7 @@ export default class EachBlock extends Node {
 		const each = this.var;
 
 		const create_each_block = this.block.name;
-		const each_block_value = this.block.listName;
+		const each_block_value = this.block.listAlias;
 		const iterations = this.iterations;
 
 		const needsAnchor = this.next ? !this.next.isDomNode() : !parentNode || !this.parent.isDomNode();


Test patch:
diff --git a/test/js/samples/deconflict-builtins/expected-bundle.js b/test/js/samples/deconflict-builtins/expected-bundle.js
new file mode 100644
--- /dev/null
+++ b/test/js/samples/deconflict-builtins/expected-bundle.js
@@ -0,0 +1,324 @@
+function noop() {}
+
+function assign(target) {
+	var k,
+		source,
+		i = 1,
+		len = arguments.length;
+	for (; i < len; i++) {
+		source = arguments[i];
+		for (k in source) target[k] = source[k];
+	}
+
+	return target;
+}
+
+function appendNode(node, target) {
+	target.appendChild(node);
+}
+
+function insertNode(node, target, anchor) {
+	target.insertBefore(node, anchor);
+}
+
+function detachNode(node) {
+	node.parentNode.removeChild(node);
+}
+
+function destroyEach(iterations) {
+	for (var i = 0; i < iterations.length; i += 1) {
+		if (iterations[i]) iterations[i].d();
+	}
+}
+
+function createElement(name) {
+	return document.createElement(name);
+}
+
+function createText(data) {
+	return document.createTextNode(data);
+}
+
+function createComment() {
+	return document.createComment('');
+}
+
+function blankObject() {
+	return Object.create(null);
+}
+
+function destroy(detach) {
+	this.destroy = noop;
+	this.fire('destroy');
+	this.set = this.get = noop;
+
+	if (detach !== false) this._fragment.u();
+	this._fragment.d();
+	this._fragment = this._state = null;
+}
+
+function _differs(a, b) {
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+}
+
+function dispatchObservers(component, group, changed, newState, oldState) {
+	for (var key in group) {
+		if (!changed[key]) continue;
+
+		var newValue = newState[key];
+		var oldValue = oldState[key];
+
+		var callbacks = group[key];
+		if (!callbacks) continue;
+
+		for (var i = 0; i < callbacks.length; i += 1) {
+			var callback = callbacks[i];
+			if (callback.__calling) continue;
+
+			callback.__calling = true;
+			callback.call(component, newValue, oldValue);
+			callback.__calling = false;
+		}
+	}
+}
+
+function fire(eventName, data) {
+	var handlers =
+		eventName in this._handlers && this._handlers[eventName].slice();
+	if (!handlers) return;
+
+	for (var i = 0; i < handlers.length; i += 1) {
+		handlers[i].call(this, data);
+	}
+}
+
+function get(key) {
+	return key ? this._state[key] : this._state;
+}
+
+function init(component, options) {
+	component._observers = { pre: blankObject(), post: blankObject() };
+	component._handlers = blankObject();
+	component._bind = options._bind;
+
+	component.options = options;
+	component.root = options.root || component;
+	component.store = component.root.store || options.store;
+}
+
+function observe(key, callback, options) {
+	var group = options && options.defer
+		? this._observers.post
+		: this._observers.pre;
+
+	(group[key] || (group[key] = [])).push(callback);
+
+	if (!options || options.init !== false) {
+		callback.__calling = true;
+		callback.call(this, this._state[key]);
+		callback.__calling = false;
+	}
+
+	return {
+		cancel: function() {
+			var index = group[key].indexOf(callback);
+			if (~index) group[key].splice(index, 1);
+		}
+	};
+}
+
+function on(eventName, handler) {
+	if (eventName === 'teardown') return this.on('destroy', handler);
+
+	var handlers = this._handlers[eventName] || (this._handlers[eventName] = []);
+	handlers.push(handler);
+
+	return {
+		cancel: function() {
+			var index = handlers.indexOf(handler);
+			if (~index) handlers.splice(index, 1);
+		}
+	};
+}
+
+function set(newState) {
+	this._set(assign({}, newState));
+	if (this.root._lock) return;
+	this.root._lock = true;
+	callAll(this.root._beforecreate);
+	callAll(this.root._oncreate);
+	callAll(this.root._aftercreate);
+	this.root._lock = false;
+}
+
+function _set(newState) {
+	var oldState = this._state,
+		changed = {},
+		dirty = false;
+
+	for (var key in newState) {
+		if (this._differs(newState[key], oldState[key])) changed[key] = dirty = true;
+	}
+	if (!dirty) return;
+
+	this._state = assign({}, oldState, newState);
+	this._recompute(changed, this._state);
+	if (this._bind) this._bind(changed, this._state);
+
+	if (this._fragment) {
+		dispatchObservers(this, this._observers.pre, changed, this._state, oldState);
+		this._fragment.p(changed, this._state);
+		dispatchObservers(this, this._observers.post, changed, this._state, oldState);
+	}
+}
+
+function callAll(fns) {
+	while (fns && fns.length) fns.shift()();
+}
+
+function _mount(target, anchor) {
+	this._fragment[this._fragment.i ? 'i' : 'm'](target, anchor || null);
+}
+
+function _unmount() {
+	if (this._fragment) this._fragment.u();
+}
+
+var proto = {
+	destroy: destroy,
+	get: get,
+	fire: fire,
+	observe: observe,
+	on: on,
+	set: set,
+	teardown: destroy,
+	_recompute: noop,
+	_set: _set,
+	_mount: _mount,
+	_unmount: _unmount,
+	_differs: _differs
+};
+
+/* generated by Svelte vX.Y.Z */
+
+function create_main_fragment(component, state) {
+	var each_anchor;
+
+	var createElement_1 = state.createElement;
+
+	var each_blocks = [];
+
+	for (var i = 0; i < createElement_1.length; i += 1) {
+		each_blocks[i] = create_each_block(component, assign({}, state, {
+			createElement: createElement_1,
+			node: createElement_1[i],
+			node_index: i
+		}));
+	}
+
+	return {
+		c: function create() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].c();
+			}
+
+			each_anchor = createComment();
+		},
+
+		m: function mount(target, anchor) {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].m(target, anchor);
+			}
+
+			insertNode(each_anchor, target, anchor);
+		},
+
+		p: function update(changed, state) {
+			var createElement_1 = state.createElement;
+
+			if (changed.createElement) {
+				for (var i = 0; i < createElement_1.length; i += 1) {
+					var each_context = assign({}, state, {
+						createElement: createElement_1,
+						node: createElement_1[i],
+						node_index: i
+					});
+
+					if (each_blocks[i]) {
+						each_blocks[i].p(changed, each_context);
+					} else {
+						each_blocks[i] = create_each_block(component, each_context);
+						each_blocks[i].c();
+						each_blocks[i].m(each_anchor.parentNode, each_anchor);
+					}
+				}
+
+				for (; i < each_blocks.length; i += 1) {
+					each_blocks[i].u();
+					each_blocks[i].d();
+				}
+				each_blocks.length = createElement_1.length;
+			}
+		},
+
+		u: function unmount() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].u();
+			}
+
+			detachNode(each_anchor);
+		},
+
+		d: function destroy$$1() {
+			destroyEach(each_blocks);
+		}
+	};
+}
+
+// (1:0) {{#each createElement as node}}
+function create_each_block(component, state) {
+	var node = state.node, node_index = state.node_index;
+	var span, text_value = node, text;
+
+	return {
+		c: function create() {
+			span = createElement("span");
+			text = createText(text_value);
+		},
+
+		m: function mount(target, anchor) {
+			insertNode(span, target, anchor);
+			appendNode(text, span);
+		},
+
+		p: function update(changed, state) {
+			node = state.node;
+			node_index = state.node_index;
+			if ((changed.createElement) && text_value !== (text_value = node)) {
+				text.data = text_value;
+			}
+		},
+
+		u: function unmount() {
+			detachNode(span);
+		},
+
+		d: noop
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+
+export default SvelteComponent;
diff --git a/test/js/samples/deconflict-builtins/expected.js b/test/js/samples/deconflict-builtins/expected.js
new file mode 100644
--- /dev/null
+++ b/test/js/samples/deconflict-builtins/expected.js
@@ -0,0 +1,123 @@
+/* generated by Svelte vX.Y.Z */
+import { appendNode, assign, createComment, createElement, createText, destroyEach, detachNode, init, insertNode, noop, proto } from "svelte/shared.js";
+
+function create_main_fragment(component, state) {
+	var each_anchor;
+
+	var createElement_1 = state.createElement;
+
+	var each_blocks = [];
+
+	for (var i = 0; i < createElement_1.length; i += 1) {
+		each_blocks[i] = create_each_block(component, assign({}, state, {
+			createElement: createElement_1,
+			node: createElement_1[i],
+			node_index: i
+		}));
+	}
+
+	return {
+		c: function create() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].c();
+			}
+
+			each_anchor = createComment();
+		},
+
+		m: function mount(target, anchor) {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].m(target, anchor);
+			}
+
+			insertNode(each_anchor, target, anchor);
+		},
+
+		p: function update(changed, state) {
+			var createElement_1 = state.createElement;
+
+			if (changed.createElement) {
+				for (var i = 0; i < createElement_1.length; i += 1) {
+					var each_context = assign({}, state, {
+						createElement: createElement_1,
+						node: createElement_1[i],
+						node_index: i
+					});
+
+					if (each_blocks[i]) {
+						each_blocks[i].p(changed, each_context);
+					} else {
+						each_blocks[i] = create_each_block(component, each_context);
+						each_blocks[i].c();
+						each_blocks[i].m(each_anchor.parentNode, each_anchor);
+					}
+				}
+
+				for (; i < each_blocks.length; i += 1) {
+					each_blocks[i].u();
+					each_blocks[i].d();
+				}
+				each_blocks.length = createElement_1.length;
+			}
+		},
+
+		u: function unmount() {
+			for (var i = 0; i < each_blocks.length; i += 1) {
+				each_blocks[i].u();
+			}
+
+			detachNode(each_anchor);
+		},
+
+		d: function destroy() {
+			destroyEach(each_blocks);
+		}
+	};
+}
+
+// (1:0) {{#each createElement as node}}
+function create_each_block(component, state) {
+	var node = state.node, node_index = state.node_index;
+	var span, text_value = node, text;
+
+	return {
+		c: function create() {
+			span = createElement("span");
+			text = createText(text_value);
+		},
+
+		m: function mount(target, anchor) {
+			insertNode(span, target, anchor);
+			appendNode(text, span);
+		},
+
+		p: function update(changed, state) {
+			node = state.node;
+			node_index = state.node_index;
+			if ((changed.createElement) && text_value !== (text_value = node)) {
+				text.data = text_value;
+			}
+		},
+
+		u: function unmount() {
+			detachNode(span);
+		},
+
+		d: noop
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+export default SvelteComponent;
\ No newline at end of file
diff --git a/test/js/samples/deconflict-builtins/input.html b/test/js/samples/deconflict-builtins/input.html
new file mode 100644
--- /dev/null
+++ b/test/js/samples/deconflict-builtins/input.html
@@ -0,0 +1,3 @@
+{{#each createElement as node}}
+	<span>{{node}}</span>
+{{/each}}
\ No newline at end of file