Name cache renames an undeclared global in a module #1753

Bug report or Feature request?

Bug report

Version (complete output of terser -V or specific git commit)

terser 5.51.2

Complete CLI command or minify() options used

terser a.js --module --mangle --name-cache cache.json
terser b.js --module --mangle --name-cache cache.json

terser input

// a.js
import process from "node:process";
export const pid = process.pid;

// b.js
export const platform = process.platform;

terser output or error

// a.js
import o from"node:process";export const pid=o.pid;

// b.js
export const platform=o.platform;

Running b.js throws ReferenceError: o is not defined.

Expected result

b.js keeps process.platform. It never declares process, so that is the global.

With a name cache, an undeclared global takes whatever name the cache holds for it. For scripts that is the point, since they share one global scope. In a module the toplevel scope is not the global scope, so the name a.js cached for its import can never be what process means in b.js. #165 was the same problem for import and export names, fixed in #166.

Sharing one cache across modules is what --mangle-props needs to keep property names consistent, and the variable names come along. It then takes one module importing a name that another module uses as a global, like process, crypto, or Buffer from the node: modules.