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

docs/compiler-api.md

@@ -83,7 +83,19 @@ interface PartialStatement <: Statement {
     name: PathExpression | SubExpression;
     params: [ Expression ];
     hash: Hash;
-
+
+    indent: string;
+    strip: StripFlags | null;
+}
+
+interface PartialBlockStatement <: Statement {
+    type: "PartialBlockStatement";
+    name: PathExpression | SubExpression;
+    params: [ Expression ];
+    hash: Hash;
+
+    program: Program | null;
+
     indent: string;
     strip: StripFlags | null;
 }

lib/handlebars/compiler/ast.js

@@ -47,6 +47,20 @@ let AST = {
     this.strip = strip;
   },
 
+  PartialBlockStatement: function(name, params, hash, program, openStrip, closeStrip, locInfo) {
+    this.loc = locInfo;
+    this.type = 'PartialBlockStatement';
+
+    this.name = name;
+    this.params = params || [];
+    this.hash = hash;
+    this.program = program;
+
+    this.indent = '';
+    this.openStrip = openStrip;
+    this.closeStrip = closeStrip;
+  },
+
   ContentStatement: function(string, locInfo) {
     this.loc = locInfo;
     this.type = 'ContentStatement';

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';
@@ -152,6 +154,11 @@ 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);
@@ -165,7 +172,7 @@ 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) {
@@ -176,9 +183,12 @@ 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

@@ -147,3 +147,17 @@ 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 new this.PartialBlockStatement(
+      openPartialBlock.name, openPartialBlock.params, openPartialBlock.hash,
+      program,
+      openPartialBlock.strip, close && close.strip,
+      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

@@ -90,6 +90,13 @@ Visitor.prototype = {
     this.acceptArray(partial.params);
     this.acceptKey(partial, 'hash');
   },
+  PartialBlockStatement: function(partial) {
+    this.acceptRequired(partial, 'name');
+    this.acceptArray(partial.params);
+    this.acceptKey(partial, 'hash');
+
+    this.acceptKey(partial, 'program');
+  },
 
   ContentStatement: function(/* content */) {},
   CommentStatement: function(/* comment */) {},

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) {

spec/ast.js

@@ -111,6 +111,16 @@ describe('ast', function() {
       testLocationInfoStorage(pn);
     });
   });
+  describe('PartialBlockStatement', function() {
+    it('provides default params', function() {
+      var pn = new AST.PartialBlockStatement('so_partial', undefined, {}, [], {}, {}, LOCATION_INFO);
+      equals(pn.params.length, 0);
+    });
+    it('stores location info', function() {
+      var pn = new AST.PartialBlockStatement('so_partial', [], {}, [], {}, {}, LOCATION_INFO);
+      testLocationInfoStorage(pn);
+    });
+  });
 
   describe('Program', function() {
     it('storing location info', function() {

spec/parser.js

@@ -113,6 +113,18 @@ describe('parser', function() {
     equals(astFor('{{> shared/partial?.bar}}'), '{{> PARTIAL:shared/partial?.bar }}\n');
   });
 
+  it('parsers partial blocks', function() {
+    equals(astFor('{{#> foo}}bar{{/foo}}'), '{{> PARTIAL BLOCK:foo PROGRAM:\n  CONTENT[ \'bar\' ]\n }}\n');
+  });
+  it('should handle parser block mismatch', function() {
+    shouldThrow(function() {
+      astFor('{{#> goodbyes}}{{/hellos}}');
+    }, Error, (/goodbyes doesn't match hellos/));
+  });
+  it('parsers partial blocks with arguments', function() {
+    equals(astFor('{{#> foo context hash=value}}bar{{/foo}}'), '{{> PARTIAL BLOCK:foo PATH:context HASH{hash=PATH:value} PROGRAM:\n  CONTENT[ \'bar\' ]\n }}\n');
+  });
+
   it('parses a comment', function() {
     equals(astFor('{{! this is a comment }}'), "{{! ' this is a comment ' }}\n");
   });

spec/partials.js

@@ -196,6 +196,67 @@ describe('partials', function() {
     handlebarsEnv.compile = compile;
   });
 
+  describe('partial blocks', function() {
+    it('should render partial block as default', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude}}success{{/dude}}',
+        [{}, {}, {}],
+        true,
+        'success');
+    });
+    it('should execute default block with proper context', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude context}}{{value}}{{/dude}}',
+        [{context: {value: 'success'}}, {}, {}],
+        true,
+        'success');
+    });
+    it('should propagate block parameters to default block', function() {
+      shouldCompileToWithPartials(
+        '{{#with context as |me|}}{{#> dude}}{{me.value}}{{/dude}}{{/with}}',
+        [{context: {value: 'success'}}, {}, {}],
+        true,
+        'success');
+    });
+
+    it('should not use partial block if partial exists', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude}}fail{{/dude}}',
+        [{}, {}, {dude: 'success'}],
+        true,
+        'success');
+    });
+
+    it('should render block from partial', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude}}success{{/dude}}',
+        [{}, {}, {dude: '{{> @partial-block }}'}],
+        true,
+        'success');
+    });
+    it('should render block from partial with context', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude}}{{value}}{{/dude}}',
+        [{context: {value: 'success'}}, {}, {dude: '{{#with context}}{{> @partial-block }}{{/with}}'}],
+        true,
+        'success');
+    });
+    it('should render block from partial with context', function() {
+      shouldCompileToWithPartials(
+        '{{#> dude}}{{../context/value}}{{/dude}}',
+        [{context: {value: 'success'}}, {}, {dude: '{{#with context}}{{> @partial-block }}{{/with}}'}],
+        true,
+        'success');
+    });
+    it('should render block from partial with block params', function() {
+      shouldCompileToWithPartials(
+        '{{#with context as |me|}}{{#> dude}}{{me.value}}{{/dude}}{{/with}}',
+        [{context: {value: 'success'}}, {}, {dude: '{{> @partial-block }}'}],
+        true,
+        'success');
+    });
+  });
+
   it('should pass compiler flags', function() {
     if (Handlebars.compile) {
       var env = Handlebars.create();

spec/tokenizer.js

@@ -214,6 +214,10 @@ describe('Tokenizer', function() {
     shouldMatchTokens(result, ['OPEN_PARTIAL', 'ID', 'SEP', 'ID', 'SEP', 'ID', 'CLOSE']);
   });
 
+  it('tokenizes partial block declarations', function() {
+    var result = tokenize('{{#> foo}}');
+    shouldMatchTokens(result, ['OPEN_PARTIAL_BLOCK', 'ID', 'CLOSE']);
+  });
   it('tokenizes a comment as "COMMENT"', function() {
     var result = tokenize('foo {{! this is a comment }} bar {{ baz }}');
     shouldMatchTokens(result, ['CONTENT', 'COMMENT', 'CONTENT', 'OPEN', 'ID', 'CLOSE']);

src/handlebars.l

@@ -80,6 +80,7 @@ ID    [^\s!"#%-,\.\/;->@\[-\^`\{-~]+/{LOOKAHEAD}
                                   return 'CLOSE_RAW_BLOCK';
                                  }
 <mu>"{{"{LEFT_STRIP}?">"         return 'OPEN_PARTIAL';
+<mu>"{{"{LEFT_STRIP}?"#>"        return 'OPEN_PARTIAL_BLOCK';
 <mu>"{{"{LEFT_STRIP}?"#"         return 'OPEN_BLOCK';
 <mu>"{{"{LEFT_STRIP}?"/"         return 'OPEN_ENDBLOCK';
 <mu>"{{"{LEFT_STRIP}?"^"\s*{RIGHT_STRIP}?"}}"        this.popState(); return 'INVERSE';

src/handlebars.yy

@@ -17,6 +17,7 @@ statement
   | block -> $1
   | rawBlock -> $1
   | partial -> $1
+  | partialBlock -> $1
   | content -> $1
   | COMMENT -> new yy.CommentStatement(yy.stripComment($1), yy.stripFlags($1, $1), yy.locInfo(@$))
   ;
@@ -79,6 +80,12 @@ mustache
 partial
   : OPEN_PARTIAL partialName param* hash? CLOSE -> new yy.PartialStatement($2, $3, $4, yy.stripFlags($1, $5), yy.locInfo(@$))
   ;
+partialBlock
+  : openPartialBlock program closeBlock -> yy.preparePartialBlock($1, $2, $3, @$)
+  ;
+openPartialBlock
+  : OPEN_PARTIAL_BLOCK partialName param* hash? CLOSE -> { name: $2, params: $3, hash: $4, strip: yy.stripFlags($1, $5) }
+  ;
 
 param
   : helperName -> $1