How do attack and damage modifiers affect Spiritual Weapon?

Question

Suppose a spellcaster has a spiritual weapon, and they are affected by some bonus and/or penalty to their attack rolls and/or weapon damage rolls. How do these effects apply to (the caster's) attack and damage rolls with the spiritual weapon?

The spell description specifies some limitations:

It strikes as a spell, not as a weapon, so for example, it can damage creatures that have damage reduction.

It does not get a flanking bonus or help a combatant get one. Your feats or combat actions do not affect the weapon.

Do bonuses and penalties to attack rolls (such as heroism or being grappled) apply to its attack rolls?

Do bonuses to "weapon damage rolls" (such as prayer or a bard's Inspire Courage) apply to its damage rolls?

If the caster is blinded, do they have a miss chance with the weapon?

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Related: Can clerics' Combat Feats be used with summoned Spiritual Weapons?

Answer 1

RevenantBacon's answer is flat out wrong. This has been explicitly clarified in the Core Rulebook FAQ:

https://paizo.com/paizo/faq/v5748nruor1fm

Ray: Do rays count as weapons for the purpose of spells and effects that affect weapons? Yes. (See also this FAQ item for a similar question about rays and weapon feats.)

For example, a bard's inspire courage says it affects "weapon damage rolls," which is worded that way so don't try to add the bonus to a spell like fireball. However, rays are treated as weapons, whether they're from spells, a monster ability, a class ability, or some other source, so the inspire courage bonus applies to ray attack rolls and ray damage rolls.

The same rule applies to weapon-like spells such as flame blade, mage's sword, and spiritual weapon--effects that affect weapons work on these spells.

Spells and effects that affect attacks rolls apply to Spiritual Weapon because you make attack rolls with it. So spells like Heroism and Prayer apply.

Spells and effects that apply only to weapon attacks also apply to Spiritual Weapon because it is a weapon-like spell. So Bard's Inspire Courage applies.

Spiritual Weapon specifically calls out that your feats and combat actions don't apply to it. So feats like Weapon Focus, Power Attack, and combat actions like feinting, charging, grappling don't affect it.

Spiritual Weapon also specifies "if [the weapon] goes out of your sight ... the weapon returns to you and hovers." So if the caster is blinded it can't attack at all.

Answer 2

Spiritual Weapon is not affected by any modifiers to your attack rolls

Per the spell description, it uses only your BAB and Wisdom bonus for its attack rolls, and its damage is strictly set to 1d8 + (caster level/3). Beneficial effects, such as Prayer or Bless are not applied, but neither do detrimental effects impede it, such as being sickened or grappled.

A weapon made of force appears and attacks foes at a distance, as you direct it, dealing 1d8 force damage per hit, + 1 point per three caster levels (maximum +5 at 15th level).

[...]

It uses your base attack bonus (possibly allowing it multiple attacks per round in subsequent rounds) plus your Wisdom modifier¹ as its attack bonus.

As you already noted, the spell calls out specifically that feats that you have or combat actions that you take do not impact the weapon in any way. In fact, what is most likely meant by "unaffected by your combat actions" was in reference to things like spells that you may have cast to buff yourself, since casting Prayer is most definitely an action. And before any chuckleheads say "but what about combat actions that my allies/enemies take?" no, those don't (or shouldn't) affect it either.

And that's where it ends, there are no further mentions in the spells description of it gaining bonuses or penalties based on any penalties you may have. The way the spell is worded implies that the weapon is its own entity (essentially being an animated object) and makes the attacks without your intercession. In fact, being knocked unconscious doesn't even end the spell, as it will continue to attack your most recently designated target until that target is dead, or the spell ends.

Each round after the first, you can use a move action to redirect the weapon to a new target. If you do not, the weapon continues to attack the previous round's target.

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¹_{It has been stated by one of the devs in a Paizo blog post (though I can't recall which one) that it would be reasonable for a table to houserule that a charisma-based caster, such as an Oracle, Spiritualist, or Medium, who gets this spell on their spell list can use their primary casting stat instead of Wisdom for the spells attack rolls, since at the time that the core book was released, they hadn't really done much with the idea that some divine casters might not use Wisdom as their casting stat. It's noticeable in later books where spells will say to use your spellcasting ability modifier instead of just calling out a specific stat.}