ATA

This was originally based on Automatic Type Acquisition, a subproject of TypeScript-Website, which powers the TypeScript Playground. What ATA does is it loads TypeScript types from jsDelivr and figures out @types/ packages for imported NPM modules.

When someone types

import chalk from "npm:chalk";

We want to provide them with nice types. That's the intent here.

Differences from ATA

This is now dramatically different from ATA because Deno is dramatically different from Node. Here are some of the differences:

• Deno relies heavily on URL (HTTP) imports. TypeScript does not support them at all: microsoft/TypeScript#35749
• Deno references NPM modules using a npm: prefix. TypeScript does not support that at all. It also supports a jsr: prefix for JSR imports. TypeScript does not support that at all.
• Deno requires Node modules be imported using the node: prefix. TypeScript does not make it easy to add that requirement.

Supporting URL imports, the npm: and jsr: prefixes, the required node: prefix, is very difficult.

Alternative paths

Deno has a Deno Language Server which implements all of its workarounds. Unfortunately, it's both written in Rust and relies on Deno itself. Using it on the frontend would be a total nonstarter - even if we were to compile it to WASM, it would be tens of megabytes.

We could run the Deno LSP on a server. This would require us to manage a lot of extra, sandboxed servers.

Workflow

Reflects reality on June 13, 2024.

flowchart TD
    RECEIVED_FILE
    ANALYZE_IMPORTS
    RECEIVED_FILE --> ANALYZE_IMPORTS
    ANALYZE_IMPORTS --> HAS_NODE_PREFIX
    HAS_NODE_PREFIX{"has node: prefix"} --> TRIGGER_LOADING_NPM_TYPES
    TRIGGER_LOADING_NPM_TYPES --> FETCH_URL[loadDependency]
    ANALYZE_IMPORTS --> HAS_NPM_PREFIX{"has npm: prefix"}
    ANALYZE_IMPORTS --> HAS_JSR_PREFIX{"has jsr: prefix"}
    ANALYZE_IMPORTS --> IS_ABSOLUTE_HTTPS_URL{"is absolute url"}
    ANALYZE_IMPORTS --> IS_RELATIVE_URL{"is relative url"}
    IS_RELATIVE_URL{"is relative url"} --> RESOLVE_TO_ABSOLUTE_URL
    RESOLVE_TO_ABSOLUTE_URL --> FETCH_URL
    HAS_NPM_PREFIX --> REWRITE_TO_ESM
    HAS_JSR_PREFIX --> REWRITE_TO_ESM
    IS_ABSOLUTE_HTTPS_URL{"is absolute https url"} --> FETCH_URL
    REWRITE_TO_ESM --> FETCH_URL
    FETCH_URL --> IS_VAL_URL
    IS_VAL_URL{"is val url"} --> FETCH_WITH_BEARER_TOKEN
    FETCH_URL --> IS_SKYPACK_URL
    IS_SKYPACK_URL{"is skypack url"} --> ADD_DTS_SUFFIX
    FETCH_URL --> FETCH
    ADD_DTS_SUFFIX --> FETCH
    FETCH --> HAS_X_TYPESCRIPT_TYPES_HEADER{"has x-typescript-types header"}
    HAS_X_TYPESCRIPT_TYPES_HEADER -->|Fetch types| FETCH
    FETCH --> IS_TYPES_NODE
    IS_TYPES_NODE{"is types node"} --> FIX_PROCESS_AND_BUFFER_GLOBALS
    FIX_PROCESS_AND_BUFFER_GLOBALS --> CREATE_FILE_WITH_FINAL_PATH
    FETCH --> CREATE_FILE_WITH_FINAL_PATH
    CREATE_FILE_WITH_FINAL_PATH --> WAS_REDIRECTED{"was redirected"}
    WAS_REDIRECTED --> CREATE_REDIRECT_FILE
    CREATE_REDIRECT_FILE --> DONE
    CREATE_FILE_WITH_FINAL_PATH --> DONE
    DONE --> RECEIVED_FILE

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