Implement partial blocks

This allows for failover for missing partials as well as limited templating ability through the `{{> @partial-block }}` partial special case.

Partial fix for #1018

lib/handlebars/compiler/compiler.js

@@ -1,3 +1,5 @@
+/* eslint-disable new-cap */
+
 import Exception from '../exception';
 import {isArray, indexOf} from '../utils';
 import AST from './ast';
@@ -157,6 +159,11 @@ Compiler.prototype = {
   PartialStatement: function(partial) {
     this.usePartial = true;
 
+    let program = partial.program;
+    if (program) {
+      program = this.compileProgram(partial.program);
+    }
+
     let params = partial.params;
     if (params.length > 1) {
       throw new Exception('Unsupported number of partial arguments: ' + params.length, partial);
@@ -170,7 +177,7 @@ Compiler.prototype = {
       this.accept(partial.name);
     }
 
-    this.setupFullMustacheParams(partial, undefined, undefined, true);
+    this.setupFullMustacheParams(partial, program, undefined, true);
 
     let indent = partial.indent || '';
     if (this.options.preventIndent && indent) {
@@ -181,9 +188,12 @@ Compiler.prototype = {
     this.opcode('invokePartial', isDynamic, partialName, indent);
     this.opcode('append');
   },
+  PartialBlockStatement: function(partialBlock) {
+    this.PartialStatement(partialBlock);
+  },
 
   MustacheStatement: function(mustache) {
-    this.SubExpression(mustache);   // eslint-disable-line new-cap
+    this.SubExpression(mustache);
 
     if (mustache.escaped && !this.options.noEscape) {
       this.opcode('appendEscaped');

lib/handlebars/compiler/helpers.js

@@ -185,3 +185,22 @@ export function prepareProgram(statements, loc) {
 }
 
 
+export function preparePartialBlock(openPartialBlock, program, close, locInfo) {
+  if (openPartialBlock.name.original !== close.path.original) {
+    let errorNode = {loc: openPartialBlock.name.loc};
+
+    throw new Exception(openPartialBlock.name.original + " doesn't match " + close.path.original, errorNode);
+  }
+
+  return {
+    type: 'PartialBlockStatement',
+    path: openPartialBlock.name,
+    params: openPartialBlock.params,
+    hash: openPartialBlock.hash,
+    program,
+    openStrip: openPartialBlock.strip,
+    closeStrip: close && close.strip,
+    loc: this.locInfo(locInfo)
+  };
+}
+

lib/handlebars/compiler/printer.js

@@ -84,6 +84,22 @@ PrintVisitor.prototype.PartialStatement = function(partial) {
   }
   return this.pad('{{> ' + content + ' }}');
 };
+PrintVisitor.prototype.PartialBlockStatement = function(partial) {
+  let content = 'PARTIAL BLOCK:' + partial.name.original;
+  if (partial.params[0]) {
+    content += ' ' + this.accept(partial.params[0]);
+  }
+  if (partial.hash) {
+    content += ' ' + this.accept(partial.hash);
+  }
+
+  content += ' ' + this.pad('PROGRAM:');
+  this.padding++;
+  content += this.accept(partial.program);
+  this.padding--;
+
+  return this.pad('{{> ' + content + ' }}');
+};
 
 PrintVisitor.prototype.ContentStatement = function(content) {
   return this.pad("CONTENT[ '" + content.value + "' ]");

lib/handlebars/compiler/visitor.js

@@ -75,35 +75,21 @@ Visitor.prototype = {
     this.acceptArray(program.body);
   },
 
-  MustacheStatement: function(mustache) {
-    this.acceptRequired(mustache, 'path');
-    this.acceptArray(mustache.params);
-    this.acceptKey(mustache, 'hash');
-  },
+  MustacheStatement: visitSubExpression,
 
-  BlockStatement: function(block) {
-    this.acceptRequired(block, 'path');
-    this.acceptArray(block.params);
-    this.acceptKey(block, 'hash');
+  BlockStatement: visitBlock,
 
-    this.acceptKey(block, 'program');
-    this.acceptKey(block, 'inverse');
-  },
+  PartialStatement: visitPartial,
+  PartialBlockStatement: function(partial) {
+    visitPartial.call(this, partial);
 
-  PartialStatement: function(partial) {
-    this.acceptRequired(partial, 'name');
-    this.acceptArray(partial.params);
-    this.acceptKey(partial, 'hash');
+    this.acceptKey(partial, 'program');
   },
 
   ContentStatement: function(/* content */) {},
   CommentStatement: function(/* comment */) {},
 
-  SubExpression: function(sexpr) {
-    this.acceptRequired(sexpr, 'path');
-    this.acceptArray(sexpr.params);
-    this.acceptKey(sexpr, 'hash');
-  },
+  SubExpression: visitSubExpression,
 
   PathExpression: function(/* path */) {},
 
@@ -121,4 +107,21 @@ Visitor.prototype = {
   }
 };
 
+function visitSubExpression(mustache) {
+  this.acceptRequired(mustache, 'path');
+  this.acceptArray(mustache.params);
+  this.acceptKey(mustache, 'hash');
+}
+function visitBlock(block) {
+  visitSubExpression.call(this, block);
+
+  this.acceptKey(block, 'program');
+  this.acceptKey(block, 'inverse');
+}
+function visitPartial(partial) {
+  this.acceptRequired(partial, 'name');
+  this.acceptArray(partial.params);
+  this.acceptKey(partial, 'hash');
+}
+
 export default Visitor;

lib/handlebars/runtime.js

@@ -194,7 +194,11 @@ export function wrapProgram(container, i, fn, data, declaredBlockParams, blockPa
 
 export function resolvePartial(partial, context, options) {
   if (!partial) {
-    partial = options.partials[options.name];
+    if (options.name === '@partial-block') {
+      partial = options.data['partial-block'];
+    } else {
+      partial = options.partials[options.name];
+    }
   } else if (!partial.call && !options.name) {
     // This is a dynamic partial that returned a string
     options.name = partial;
@@ -209,6 +213,15 @@ export function invokePartial(partial, context, options) {
     options.data.contextPath = options.ids[0] || options.data.contextPath;
   }
 
+  let partialBlock;
+  if (options.fn && options.fn !== noop) {
+    partialBlock = options.data['partial-block'] = options.fn;
+  }
+
+  if (partial === undefined && partialBlock) {
+    partial = partialBlock;
+  }
+
   if (partial === undefined) {
     throw new Exception('The partial ' + options.name + ' could not be found');
   } else if (partial instanceof Function) {