nREPL and ClojureScript: Demystifying Piggieback

A deep-dive into Piggieback, the nREPL middleware that enables ClojureScript evaluation over a standard nREPL server. The author explains how Piggieback hijacks nREPL sessions to reroute eval messages to a JavaScript runtime (Node, browser, etc.) via ClojureScript's IJavaScriptEnv protocol, without requiring any client-side changes. Key internals covered include session-based dispatch, the DelegatingReplEnv trick to prevent premature teardown, how the compiler environment is stashed for use by tools like cider-nrepl, and the two distinct code paths for REPL setup vs. steady-state evaluation. The post also covers known limitations (one Node REPL per JVM, no interrupt support, multi-form eval), contrasts Piggieback's approach with shadow-cljs, and summarizes recent 0.6.x/0.7.0 bug fixes and refactoring work done as part of the CIDER 2.0 effort.

Nguồn: https://metaredux.com/posts/2026/07/01/demystifying-piggieback.html. 8sync News chỉ tóm tắt và dẫn link; bản quyền nội dung thuộc tác giả và nguồn gốc.

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CIDER 2.0 is Brewing...

CIDER, the Clojure interactive development environment for Emacs, is getting a major version bump to 2.0. Key additions include transient-based discoverable keymaps, a unified foldable tree-view widget across all browsers, built-in cross-reference/call-graph functionality (reducing need for clj-refactor.el or clojure-lsp), a revamped debugging toolbox with inline macro stepping and a dedicated trace buffer, ClojureScript test and macroexpansion fixes, async Eldoc, and numerous quality-of-life improvements. The snapshot is available on MELPA now, with the official release expected in a week or two. The author credits AI agents for helping prototype ideas faster, while noting design decisions remain his own.

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