Can an Eldritch Knight use the bonus-action attack granted by War Magic before casting the spell as an action?

Question

A Fighter with the Eldritch Knight martial archetype gets the feature War magic at 7th level (and Improved War Magic at 18th level). The War Magic feature (PHB, p. 75) states:

Beginning at 7th level, when you use your action to cast a cantrip, you can make one weapon attack as a bonus action.

The Improved War Magic feature changes "cantrip" to "spell", allowing you to cast a leveled spell as an action and make a weapon attack as a bonus action on the same turn.

Can I use this bonus-action attack before I cast the cantrip (spell)? That is, can I state that I'm going to cast a spell with my action, and thus be granted a bonus action, then use it to make a weapon attack, and then cast the spell as my action?

The rules for bonus action timing state:

You choose when to take a bonus action during your turn, unless the bonus action's timing is specified.

I'm not sure if the wording of War Magic counts as specifying the timing.

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Motivation:

If this is possible, it would be especially interesting if used together with the Eldritch Knight's 10th-level feature Eldritch Strike, granting you its bonus on your first action, instead of your second. Eldritch Strike states:

When you hit a creature with a weapon attack, that creature has disadvantage on the next saving throw it makes against a spell you cast before the end of your next turn.

Answer 1

Nope. You only get the bonus action when you use your action to cast a cantrip. You can't use the granted bonus action before you cast the cantrip, because you haven't done the thing that grants it yet.

In case it needs saying explicitly: War Magic does specify the timing of taking the bonus action. It does it by using the word “when”, indicating that it is can only be taken at or after that time. Before that “when” you don't have that bonus action option at all.

Answer 2

Probably after, but honestly, it doesn't matter

Sage Advice Compendium version 2.2 clarifies that the bonus action comes after:

Does the “when” in the Eldritch Knight’s War Magic feature mean the bonus attack comes after you cast the cantrip, or can it come before? The bonus action comes after the cantrip, since using your action to cast a cantrip is what gives you the ability to make the weapon attack as a bonus action.

However, it says the order can easily be reversed:

a DM would break nothing in the system by allowing an Eldritch Knight to reverse the order of the cantrip and the weapon attack

This complies with RAI, according to J. Crawford in the Rules answers: June 2016 -

Does the “when” in the Eldritch Knight’s War Magic feature mean the bonus attack comes after you cast the cantrip, or can it come before? The intent is that the bonus attack can come before or after the cantrip.

Generally you can choose the timings unless a description says otherwise:

You choose when to take a bonus action during your turn, unless the bonus action specifies when it must take place (PH, 189).

Answer 3

No, you must cast the spell as your action first before making the bonus-action weapon attack.

This question is directly addressed in the Sage Advice Compendium, as of 2017:

Does the “when” in the Eldritch Knight’s War Magic feature mean the bonus attack comes after you cast the cantrip, or can it come before?

The bonus action comes after the cantrip, since using your action to cast a cantrip is what gives you the ability to make the weapon attack as a bonus action. That said, a DM would break nothing in the system by allowing an Eldritch Knight to reverse the order of the cantrip and the weapon attack.

This contrasts with Jeremy Crawford's prior ruling on the bonus action granted by that feature (and similar ones, such as Shield Master and Crossbow Expert). He had previously ruled - as addressed in the 2016 version of the Sage Advice Compendium - that:

The intent is that the bonus attack can come before or after the cantrip. You choose when to take a bonus action during your turn, unless the bonus action specifies when it must take place (PH, 189).

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In fact, this exact change in ruling prompted a broader change in rulings regarding conditional bonus actions (such as the bonus-action shove granted by the Shield Master feat or the bonus-action attack from Crossbow Expert). Jeremy Crawford explained the new ruling here on Twitter:

Clarification about bonus actions: if a feature says you can do X as a bonus action if you do Y, you must do Y before you can do X. For Shield Master, that means the bonus action must come after the Attack action. You decide when it happens afterward that turn.

Crawford acknowledged his change in rulings here, specifically mentioning his changed ruling on War Magic as the one that reflected his logical interpretation of the wording:

In 2017, I changed the ruling on bonus action timing because the old ruling was illogical. The original ruling failed to account for the fact that X relying on Y is a form of timing. The new ruling corrects that oversight.

He further explained his reasoning here:

The old ruling on bonus action timing didn't quiet questions on that timing. Instead, the illogical ruling fueled questions, and it even inadvertently led some fans to think our choice of words like "if" or "when" had super-precise meanings in bonus actions. They don't.

Answer 4

This feature uses the same wording as the shield master feat which can be used before or after according to Jeremy Crawford. So, yes, you can use your bonus action before.

Contrast this with the Flurry of Blows feature that specifies "after".

Answer 5

Yes, you can. The Basic Rules PDF states under Bonus Actions, emphasis added:

You choose when to take a bonus action during your turn, unless the bonus action’s timing is specified, and anything that deprives you of your ability to take actions also prevents you from taking a bonus action.

Since the timing is not specified in War Magic, you choose when to use the bonus action.