Import-maps does not work in dynamic imports import()

[tani]

Import map is an option to rewrite the module path to another.
For instance, By "npm:" : "https://esm.sh/", the runtime changes the path "npm:diff" to "https://esm.sh".

parent.ts + import-maps
|---------------------(import)
+-- child.ts
     |----------------(import)
     +-- `npm:diff` ===> `https://esm.sh/diff`

I noticed that the import-map is unavailable in the following situation.

parent.ts + import-maps
|---------------------(dynamic import)
+-- child.ts
     |----------------(import)
     +-- `npm:diff` =x=> `https://esm.sh/diff`

Expected behavior

According to the specification, "Only one import map is processed per Document.".
The parent module shares the document context with the child one.
Thus, the parent module should share the import-maps with the child one too.

Reproducible steps

{
   "imports": {
     "npm:": "https://esm.sh/"
   }
}

await import(new URL('child.ts', import.meta.url))

import * as diff from "npm:diff"
diff;

Significance of this issue

#15826 , the developers have no plan to support "npm:" modules in the dynamic import.
However, we sometime need to dynamically import the third-party module depending the "npm:" module.
Further, we have no way to know which module has no dependency to "npm:" module in advance.
Therefore, to avoid "npm:" module temporally, we need to define such a rule.

Related issues

• Import map not working with Worker #6675 , the parent module does not shares the document context with the worker. Thus, that issue should be discussed separately with this issue.
• Loading npm specifiers in dynamic import that's non-analyzable when other code does not have npm specifiers is somewhat broken #15826 , Please see the previous section.