One of the uses of the wish spell is to emulate any spell of 8th level or lower "without meeting any requirements" of that spell. It is already clear from wish's description that costly material components are to be discarded, but what about other requirements of a spell?
In general, what is considered a requirement of a spell for the purposes of wish?
Wish lets you ignore the requirements of:
Requirements, unfortunately, is never really given a game term definition.
So as with all words that don't have a game term definition, we should attempt to use the standard english definition.
Using that, we can say that anything is a requirement if it prevents you from casting the spell.
So with that in mind, here's the justification:
[Level] [School] - If a spell is not normally of the right level or school for you, you cannot cast it. This is a "requirement".
Casting Time: x - If you do not spend the amount of time specified, you cannot cast it. This is a "requirement".
Range: x Having nothing in range does not actually prevent you from casting a spell (for example, readying) - it prevents you from targeting it. This is NOT a "requirement".
Components: x, y, z (special) - if you cannot provide the proper components, you cannot cast the spell. This is a "requirement".
Duration: x - duration has nothing to do with whether you're capable of casting a spell. This is NOT a "requirement".
Concentration - When casting a spell normally, you can choose not to maintain concentration. The spell will end, but you are not prevented from casting it. This is NOT a "requirement".
Classes: x - If a spell is not on your prepared or known spells, you cannot cast it. This is a "requirement".
Description: [Effects] - Effects can only take place after casting is completed. This is NOT a "requirement".
Spell Slot - If you cannot provide the right spell slot, you cannot cast a spell. This is a "requirement".
Specific features (in addition to Wish) can negate some or all of these requirements, or even add requirements: see Subtle Spell or Ritual Casting
The rules do not describe what "requirement" means: it's not a game term the way "attack" or "spell" are. This means that differing DMs may interpret what a requirement is in the context of wish in slightly different ways.
However, as with all words that are not a game term, we can attempt to use the standard English definition. In this case: "a thing that is compulsory; a necessary condition."
We should try to contextualize that generic definition. When wish is used to duplicate a spell, "the spell simply takes effect". With this in mind I believe that "any condition you normally must satisfy for a spell to take effect" is a requirement that wish ignores.
The spell's effect is not a requirement. Rather, it is what wish duplicates.
Casting time is a requirement which wish ignores, because you normally must spend a certain amount of time casting for a spell to take effect.
Components are requirements which wish ignores, because you normally must provide/handle/perform components for a spell to take effect.
Duration is not a requirement, because it only defines how long the spell effect lasts. The same is true for concentration, it only defines how long the spell effect lasts.
Having the spell firmly fixed in mind is a requirement which wish ignores, because you normally must learn or prepare a spell to cast it. This goes along with the fact that wish explicitly "duplicate[s] any other spell of 8th level or lower".
Spell slots are requirements which wish ignores, because you normally must expend a spell slot for a spell to take effect.
The spell's level is not a requirement, because it just indicates how powerful the spell is. Moreover, wish explicitly limits you to "spell[s] of 8th level or lower", so either way wish does not ignore the spell's level.
The spell's school is not a requirement. Rather it is a description of the spell's effect.
Targeting restrictions are requirements which wish ignores1, because you normally must target something for the spell to take effect. This includes rules for range and other requirements described in the spell, such as sight and shared language.
Rules for a clear path to the target are more nuanced: AoE spells take effect even if the target is behind total cover, so a clear path to the target is not a requirement for AoE spells. However, it is still a requirement for other spells.
This answer is based in part on a different answer by Speedkat.
Wish can be cast to emulate spells the caster normally wouldn't be able to cast; i.e., not in their spellbook if they're a Wizard, Cleric Only Spell for non-Cleric, etc. Any spell means what it says: any spell.
What is a spell? A spell is a spell on a spell list that creates a magical effect.
By simply speaking aloud (components are replaced by simply speaking aloud) ... duplicate any other spell of 8th level or lower. You don’t need to meet any requirements in that spell, including costly components. The spell simply takes effect. (wish, spell description, PHB)
No mention is made of casting time; the text of the wish spell casting time is "1 action" and "by simply speaking aloud" the desired spell "simply takes effect."
Just say it, and it takes effect.
What constraints on a spell might be in play when used like this? Since it duplicates a given spell, you would expect the duplicated spell cast by wish to have the same range and area of effect. Nowhere does wish indicate that it changes a spell when cast this way.
First, consider the relevant effect of wish:
The basic use of this spell is to duplicate any other spell of 8th level or lower. You don't need to meet any requirements in that spell, including costly components. The spell simply takes effect.
“Duplicate” here indicates that wish produces exactly the effect of the duplicated spell. Duplicating a spell with wish cannot do anything except for producing an exact duplicate of the spell’s effect. If, hypothetically, we change any portion of the spell’s effect, we are not duplicating that spell. This, of course, begs the question “what exactly is a spell’s effect?” Fortunately, the rules tell us exactly what a spell’s effect is:
Each spell description in Chapter 11 begins with a block of information, including the spell’s name, level, school of magic, casting time, range, components, and duration. The rest of a spell entry describes the spell’s effect.
The “rest of a spell entry” here refers to the block of text that follows “ the spell’s name, level, school of magic, casting time, range, components, and duration.” Ergo, duplicating a spell with wish cannot change anything in this block of text, since this block of text is exactly the spell’s effect that is duplicated.
So we conclude that the requirements that are ignored by wish are anything else that is usually necessary for casting the spell that is not contained in this block of text.
Under "Chapter 10: Spellcasting", the PHB and Basic Rules list parts of the spells and mention requirements.
Casting Time (p. 202):
Most spells require a single action to cast, but some spells require a bonus action, a reaction, or much more time to cast.
Components (p. 203):
A spell’s components are the physical requirements you must meet in order to cast it.
Concentration (p. 203):
Some spells require you to maintain concentration in order to keep their magic active.
Targets (p. 204):
A typical spell requires you to pick one or more targets to be affected by the spell’s magic.
and Attack Rolls (p. 205):
Some spells require the caster to make an attack roll to determine whether the spell effect hits the intended target.
Therefore, the casting time of the recreated spell becomes the 1 action of wish. Components become the verbal component of wish. Spells that normally require concentration automatically last their full duration without concentration and attack spells (not area effect spells) automatically hit.
The only vagueness up for DM discretion and discussion that I really see is "targets".
I should note that range isn't a "requirement" and stays the same, so spells with a range of Self still only target or originate from you.
