fix(cli): correctly nest @media rules inside parent selectors (#10375)

[mrlexcoder]

Problem

When a registry item (e.g., registry:style) defines nested at-rules like @media inside a selector object (e.g., body inside @layer base), the PostCSS merger in the CLI incorrectly appends those @media blocks as siblings to the parent at-rule instead of nesting them inside the current rule.

Example registry item:

{
  "name": "repro-nested-media",
  "type": "registry:style",
  "css": {
    "@layer base": {
      "body": {
        "--foo": "1rem",
        "@media (width >= 40rem)": {
          "--foo": "2rem"
        }
      }
    }
  }
}

Current (broken) output:

@layer base {
  body {
    --foo: 1rem;
  }
  @media (width >= 40rem) {
     --foo: 2rem;
  }
}

This causes "Unexpected end of input" errors in Next.js because the @media rule is orphaned outside the body selector.

Expected output:

@layer base {
  body {
    --foo: 1rem;
    @media (width >= 40rem) {
      --foo: 2rem;
    }
  }
}

Root Cause

In packages/shadcn/src/utils/updaters/update-css.ts, the processRule function handles nested objects (line 597-602). When it encounters a nested object property, it assumes it's a nested selector and calls processRule(parent, ...), which appends to the parent at-rule instead of the current rule.

The code didn't check if the nested property is an at-rule (starts with @) with a body.

Solution

Added logic to detect nested at-rules with bodies:

1. Check if prop.startsWith("@") and has a non-empty object value
2. Create the at-rule inside the current rule (not parent)
3. Recursively process the nested content inside the at-rule

Changes

• packages/shadcn/src/utils/updaters/update-css.ts - Updated processRule function (lines 597-624)

Testing

With this fix:

• Nested @media rules are correctly placed inside their parent selectors
• No more "Unexpected end of input" errors
• Works with any nested at-rule (@media, @supports, @container, etc.)

Related

Fixes #10375

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Submitted by: @mrlexcoder

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