@openrewrite/rewrite

Greetings!

The OpenRewrite project is a mass refactoring ecosystem designed to eliminate technical debt across an engineering organization. Full documentation and information is available at OpenRewrite.

This project contains the LST models as well as the runtime required to execute OpenRewrite recipes.

How to install

npm i -D @openrewrite/rewrite

Inspecting type attribution

Most recipe debugging is one question: what type did this expression get, and if none, where was it lost? Set REWRITE_JAVASCRIPT_DUMP_TYPES and any RecipeSpec test prints the attribution its own parse produced, which is the attribution a MethodMatcher pattern written for that test has to match:

$ REWRITE_JAVASCRIPT_DUMP_TYPES=1 npx vitest run test/my-recipe.test.ts

--- type attribution: source-0.ts ---
line:col  kind                   source                      type
1:1       MethodDeclaration      function f(arr, s: string)  source-0 f(..) -> <unknown>
1:12      NamedVariable          arr                         ⚠ <unknown>
1:16      NamedVariable          s: string                   String
2:5       MethodInvocation       s.charAt(0)                 String charAt(number) -> String
2:14        └ arg0:Literal       0                           double (Primitive)
3:12      MethodInvocation       arr.tostring()              ⚠ <unknown> tostring(..) -> <unknown>
3:12        └ select:Identifier  arr                         <unknown>

The text before -> is a pattern that new MethodMatcher(...) or usesMethod(...) accepts for that call. It names the resolved overload's parameter types where the matcher can, and (..) where one has no name it compares. A type without a package, such as Array, matches only the type of that name in no package, and *.Array matches it in any package. Each pattern is checked against the matcher, and a call whose pattern cannot match it, such as one declared on an anonymous class, carries a note saying so.

The arg rows give each argument's type and its kind, which is what a capture constraint over that argument reads. Patterns spell primitives the TypeScript way, which the matcher accepts. The type column and arg rows use the model's names, so a number is the primitive double and a string is String. A kind only JavaScript has carries its namespace, as in JS.Binary, since a visitor reaches it through a method of its own.

arr.tostring() has no declaring type, and the indented select row names the receiver that lost it. <none> is a slot the parser left empty and <unknown> is Type.unknownType.

The variable accepts comma-separated flags. missing lists only unattributed nodes, all widens the listing beyond calls and declarations, and supertypes shows each declaring type's superclass chain, whose types a matchOverrides pattern may name.

A recipe gated on a type that never resolved is the usual reason a test sees no change, so that failure names the unattributed nodes without being asked:

Nodes with no type attribution (a recipe gated on one of these cannot fire):
  line:col  kind                   source          type
  1:12      NamedVariable          arr             ⚠ <unknown>
  3:12      MethodInvocation       arr.tostring()  ⚠ <unknown> tostring(..) -> <unknown>
  3:12        └ select:Identifier  arr             <unknown>

npx rewrite-javascript-types <file> runs the same report on a file on disk. It resolves node_modules and tsconfig.json from the nearest directory with a package.json, or from --project-root. A project without its dependencies installed attributes differently from a test, so prefer the test output when writing a pattern for a test.

To see what a recipe's output carries, call printTypes from a spec's afterRecipe hook. From code, printTypes(sourceFile) writes the same listing, buildTypeReport(sourceFile) returns it as data, and new LstDebugPrinter({includeTypes: true}) adds types to the tree view.

When making changes to JavaScript code

You can run this command from rewrite/ directory to build the JavaScript code. A subsequent run of JavaScriptRewriteRpc will use that.

npm run build

Alternatively, ./gradlew npmBuild.