Parser
The sourcecode for the TypeScript parser is located entirely in
parser.ts
. Scanner is controlled internally by the Parser
to convert the source code to an AST. Here is a review of what the desired outcome is.SourceCode ~~ scanner ~~> Token Stream ~~ parser ~~> AST
The parser is implemented as a singleton (similar reasons to
scanner
, don't want to recreate it if we can reinit it). It is actually implemented as namespace Parser
which contains state variables for the Parser as well as a singleton scanner
. As mentioned before it contains a const scanner
. The parser functions manage this scanner.Parser is driven indirectly by Program (indirectly as its actually by
CompilerHost
which we mentioned previously). Basically this is the simplified call stack:Program ->
CompilerHost.getSourceFile ->
(global function parser.ts).createSourceFile ->
Parser.parseSourceFile
The
parseSourceFile
not only primes the state for the Parser but also primes the state for the scanner
by calling initializeState
. It then goes on to parse the source file using parseSourceFileWorker
.Before we dig too deep into the parser internals, here is a sample code that uses the TypeScript's parser to get the AST of a source file (using
ts.createSourceFile
), and then print it.code/compiler/parser/runParser.ts
import * as ts from "ntypescript";
function printAllChildren(node: ts.Node, depth = 0) {
console.log(new Array(depth + 1).join('----'), ts.formatSyntaxKind(node.kind), node.pos, node.end);
depth++;
node.getChildren().forEach(c=> printAllChildren(c, depth));
}
var sourceCode = `
var foo = 123;
`.trim();
var sourceFile = ts.createSourceFile('foo.ts', sourceCode, ts.ScriptTarget.ES5, true);
printAllChildren(sourceFile);
This will print out the following:
SourceFile 0 14
---- SyntaxList 0 14
-------- VariableStatement 0 14
------------ VariableDeclarationList 0 13
---------------- VarKeyword 0 3
---------------- SyntaxList 3 13
-------------------- VariableDeclaration 3 13
------------------------ Identifier 3 7
------------------------ FirstAssignment 7 9
------------------------ FirstLiteralToken 9 13
------------ SemicolonToken 13 14
---- EndOfFileToken 14 14
This looks like a (very right sided) tree if you tilt your head to the left.
Last modified 4yr ago