using le as a pronoun

Question

I should know this, but can you tell me when using le as a pronoun which comes after the preposition 'de' is the rule that it never becomes' Du'?

I incorrectly did that with the following sentence

Mais quand ma meilleure amie Miriam a décidé de le faire

Accepted Answer

Bonjour Mark,
‘de’ here is a preposition used to help introduce a verb (‘faire’). It is not a part of the partitive article as it doesn’t imply a quantity of an item, even if there is ‘le’ after it.
Here is a link with a list of verbs that follow the same pattern as ‘décider de + infinitif’: Verbs + de + [infinitive]
‘le’ is a direct object pronoun of the verb ‘faire’ and it refers to ‘to go study abroad’.
Here is a link on this specific topic: when-to-use-le-la-l-or-les-to-replace-nouns-direct-object-pronouns
Here is another link to partitive articles: french-partitive-articles
I hope this is helpful.
Bonne journée!

Answer

Simple rule:

If le is followed by a noun: de + le + noun --> du + noun. (contracts)
If le is followed by a verb: de + le + verb --> de + le + verb. (remains unchanged)

In other words, only if le is used as an article -- and not as a pronoun -- does it contract with a preceding de.