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Internal design

TypeScript compiler

tslab depends on a branched version of TypeScript (@tslab/typescript-for-tslab) to use unexported APIs of TypeScript compiler. See README of the branched version for details of modifications. At the same time, tslab also dev-depends on the mainline TypeScript to compile src code and run tests with ts-jest.

Also, tslab has @types/node as dependencies, not devDependencies. This is intentional to fix #10.

Code executor

runInThisContext and how to share variables amoung cells

To share variables among code cells, tslab converts references to variables defined in previous cells (e.g. x + y) to references to properties of exports (e.g. exports.x + exports.y) before running code in vm.runInThisContext.

  • getCustomTransformers in src/converter.ts
  • vm.runInThisContext in src/executor.ts

Previously, tslab used vm.runInContext with a customized context which hooks accesses to variables defined in previous cells. But tslab switched to the current approach with vm.runInThisContext to avoid problems like #32.

exports

  • exports is defined as a Proxy
  • It forwards assigned variables to locals to share exported variables among cells.
  • We don't expose locals as exports directly because irreversible operations (e.g. Object.defineProperty(exports, "__esModule", { value: true });) can be applied to exports but we don't want to share the results of irreversible operations among cells.

Registeration to Jupyter

tslab install registers tslab command to Jupyter environment. This behavior requires users to install tslab in a directory in PATH environment variable. Initially, tslab install registered the absolute path of bin/tslab to Jupyter. But I simplified it to support Windows (commit).