The usage of な to make an entire clause modify a noun, and "Alice is a desirable person" versus "Person that likes Alice"

Question

In the very beginning of Tae Kim's Guide to Japanese, namely here, there is this example:

魚が好きな人。

Person that likes fish.

When I read that for the first time, still as a very beginner in japanese, I just said "ok interesting, let's move on". But now, having completed the whole "Basic Grammar" and "Essential Grammar" sections of Tae Kim's guide, and drastically improved my vocabulary, I decided to reread everything and stumbled at this example.

It sounded unnatural, strange. As if the phrase was saying "fish is desirable person". (Note: of course I am far from fluent, so I wouldn't be surprised if it's correct, although sounding strange).

So I see two ways of parsing that phrase:

• (魚が好き)な人
• 魚が(好きな人)

Question 1: As far as I know (and here is where I'm probably wrong), we should use な to connect na-adjectives to nouns, but the first way of parsing is using な to connect a whole clause to a noun, is this grammar really correct? Does the whole clause accept a な simply because it ends in a na-adjective? What is going on here?

Question 2: Clearly the second option ("fish is desirable person") does not make sense, but I think we can create a similar example in which both interpretations would fit:

• "person that likes Alice": (Aliceが好き)な人
• "Alice is (a) desirable person": Aliceが(好きな人)

If this is correct, then is guessing by context the only way to decide between the two interpretations?

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Note: I didn't post these as separate questions because they are extremely related and there is a chance that a single explanation might help me with both questions.

Answer 1

Question 1

As Tae Kim's guide says, relative clauses cannot end with だ, so you cannot say 魚が好きだ人.

The negative, past, and negative past conjugations of verbs can be used just like adjectives to directly modify nouns. However, we cannot do this with the plain non-past state-of-being using 「だ」. (I told you this was a pain in the butt.) The language has particles for this purpose, which will be covered in the next section.

And in the next page, it says you need to use な for cases involving na-adjectives anyway:

Even when substituting 「の」 for a noun, you still need the 「な」 to modify the noun when a na-adjective is being used.

Apparently that page lacks an example for this pattern, but basically whenever you can say A + は + B + が + na-adj, you can turn it into a relative clause and say B + が + na-adj + な + A (or rarely, A + が + na-adj + な + B, as described below).

• そのスマホはCPUが高性能だ。 (The smartphone has a high-performance CPU.)
  → CPUが高性能なスマホ (a smartphone with a high-performance CPU)
• その生徒は成績が優秀で将来が有望だ。(The student is academically excellent and his future is promising.)
  → 成績が優秀で将来が有望な生徒 (a student with high grades and promising future)

Question 2

アリスが好きな人 is indeed ambiguous and means both "a person whom Alice likes" and "a person who likes Alice". This ambiguity has been asked several times, so please read my previous answer.

Answer 2

Question 1: "is this grammar really correct?"
Yes, it is correct.
According to "A Dictionary of Basic Japanese Grammar", page 376, there are 3 ways of forming the relative clause:

1. Verb/i-adjective + noun
   Examples: 話す人。話した人。高い本。高かった本。

2. na-adjective + な/だった + noun
   Examples: 静かな家。静かだった家。

3. noun + の/だった/である/であった + noun
   Examples: 先生である田中さん。

So in your example な connects the whole clause to a noun.

Question 2:
魚が好きな人。is actually ambiguous and can have 2 interpretations:
A person that likes fish.
A person that is liked by the fish.

Does the person like the fish or does the fish like the person?
The relative clause is actually ambiguous and only the context can tell you which interpretation is correct.