Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
1 changed file
with
224 additions
and
0 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,224 @@ | ||
# Handlebars Compiler APIs | ||
|
||
There are a number of formal APIs that tool implementors may interact with. | ||
|
||
## AST | ||
|
||
Other tools may interact with the formal AST as defined below. Any JSON structure matching this pattern may be used and passed into the `compile` and `precompile` methods in the same way as the text for a template. | ||
|
||
AST structures may be generated either with the `Handlebars.parse` method and then manipulated, via the `Handlebars.AST` objects of the same name, or constructed manually as a generic JavaScript object matching the structure defined below. | ||
|
||
```javascript | ||
var ast = Handlebars.parse(myTemplate); | ||
|
||
// Modify ast | ||
|
||
Handlebars.precompile(ast); | ||
``` | ||
|
||
|
||
### Basic | ||
|
||
```java | ||
interface Node { | ||
type: string; | ||
loc: SourceLocation | null; | ||
} | ||
|
||
interface SourceLocation { | ||
source: string | null; | ||
start: Position; | ||
end: Position; | ||
} | ||
|
||
interface Position { | ||
line: uint >= 1; | ||
column: uint >= 0; | ||
} | ||
``` | ||
|
||
### Programs | ||
|
||
```java | ||
interface Program <: Node { | ||
type: "Program"; | ||
body: [ Statement ]; | ||
|
||
blockParams: [ string ]; | ||
strip: StripFlags | null; | ||
} | ||
``` | ||
|
||
### Statements | ||
|
||
```java | ||
interface Statement <: Node { | ||
strip: StripFlags | null; | ||
} | ||
|
||
interface MustacheStatement <: Statement { | ||
type: "MustacheStatement"; | ||
sexpr: Subexpression; | ||
escaped: boolean; | ||
} | ||
|
||
interface BlockStatement <: Statement { | ||
type: "BlockStatement"; | ||
sexpr: Subexpression; | ||
program: Program; | ||
inverse: Program | null; | ||
} | ||
|
||
interface PartialStatement <: Statement { | ||
type: "PartialStatement"; | ||
sexpr: Subexpression; | ||
|
||
indent: string; | ||
} | ||
|
||
interface ContentStatement <: Statement { | ||
type: "ContentStatement"; | ||
value: string; | ||
original: string; | ||
} | ||
|
||
interface CommentStatement <: Statement { | ||
type: "CommentStatement"; | ||
value: string; | ||
} | ||
``` | ||
|
||
### Expressions | ||
|
||
```java | ||
interface Expression <: Node { } | ||
``` | ||
|
||
##### Subexpressions | ||
|
||
```java | ||
interface SubExpression <: Expression { | ||
type: "SubExpression"; | ||
path: PathExpression; | ||
params: [ Expression ]; | ||
hash: Hash; | ||
|
||
isHelper: true | null; | ||
} | ||
``` | ||
|
||
`isHelper` is not required and is used to disambiguate between cases such as `{{foo}}` and `(foo)`, which have slightly different call behaviors. | ||
|
||
##### Paths | ||
|
||
```java | ||
interface PathExpression <: Expression { | ||
type: "PathExpression"; | ||
data: boolean; | ||
depth: uint >= 0; | ||
parts: [ string ]; | ||
original: string; | ||
} | ||
``` | ||
|
||
- `data` is true when the given expression is a `@data` reference. | ||
- `depth` is an integer representation of which context the expression references. `0` represents the current context, `1` would be `../`, etc. | ||
- `parts` is an array of the names in the path. `foo.bar` would be `['foo', 'bar']`. Scope references, `.`, `..`, and `this` should be omitted from this array. | ||
- `original` is the path as entered by the user. Separator and scope references are left untouched. | ||
|
||
|
||
##### Literals | ||
|
||
```java | ||
interface Literal <: Expression { } | ||
|
||
interface StringLiteral <: Literal { | ||
type: "StringLiteral"; | ||
value: string; | ||
original: string; | ||
} | ||
|
||
interface BooleanLiteral <: Literal { | ||
type: "BooleanLiteral"; | ||
value: boolean; | ||
original: boolean; | ||
} | ||
|
||
interface NumberLiteral <: Literal { | ||
type: "NumberLiteral"; | ||
value: number; | ||
original: number; | ||
} | ||
``` | ||
|
||
|
||
### Miscellaneous | ||
|
||
```java | ||
interface Hash <: Node { | ||
type: "Hash"; | ||
pairs: [ HashPair ]; | ||
} | ||
|
||
interface HashPair <: Node { | ||
type: "HashPair"; | ||
key: string; | ||
value: Expression; | ||
} | ||
|
||
interface StripFlags { | ||
left: boolean; | ||
right: boolean; | ||
} | ||
``` | ||
|
||
`StripFlags` are used to signify whitespace control character that may have been entered on a given statement. | ||
|
||
TODO : Document what the flags mean or drop this from things like Program. | ||
|
||
## AST Visitor | ||
|
||
`Handlebars.Visitor` is available as a base class for general interaction with AST structures. This will by default traverse the entire tree and individual methods may be overridden to provide specific responses to particular nodes. | ||
|
||
Recording all referenced partial names: | ||
|
||
```javascript | ||
var Visitor = Handlebars.Visitor; | ||
|
||
function ImportScanner() { | ||
this.partials = []; | ||
} | ||
ImportScanner.prototype = new Visitor(); | ||
|
||
ImportScanner.prototype.PartialStatement = function(partial) { | ||
this.partials.push({request: partial.sexpr.original}); | ||
|
||
Visitor.prototype.PartialStatement.call(this, partial); | ||
}; | ||
|
||
var scanner = new ImportScanner(); | ||
scanner.accept(ast); | ||
``` | ||
|
||
## JavaScript Compiler | ||
|
||
The `Handlebars.JavaScriptCompiler` object has a number of methods that may be customized to alter the output of the compiler: | ||
|
||
```javascript | ||
function MyCompiler() { | ||
Handlebars.JavaScriptCompiler.apply(this, arguments); | ||
} | ||
MyCompiler.prototype = Object.create(Handlebars.JavaScriptCompiler); | ||
|
||
MyCompiler.nameLookup = function(parent, name, type) { | ||
if (type === 'partial') { | ||
return 'MyPartialList[' + JSON.stringify(name) ']'; | ||
} else { | ||
return Handlebars.JavaScriptCompiler.prototype.nameLookup.call(this, parent, name, type); | ||
} | ||
}; | ||
|
||
var env = Handlebars.create(); | ||
env.JavaScriptCompiler = MyCompiler; | ||
env.compile('my template'); | ||
``` |