AbdulAlhazred
Legend
You mean a rule like this? From GG's DMG? That I already quoted, above?
"It can thus be understood that spell casting during a melee can be a tricky business, for a mere shove at any time can spoil the dweomer!"
You're IMHO confusing commentary with a RULE. This is stating that it 'can' (this should be MAY or IS really) be tricky. Thus there is SOMEWHERE a rule which describes mechanically how it is tricky.
1EPHB100 said:Most spells can be cost during the course of a single melee round,
although some - porticularly high level ones - require more time.
Casting a spell requires certain actions, and if these are interrupted, the
spell cannot be cast and it is lost from memory. A good example of this is a
magic-user about to cost a fireball spell being struck by on arrow when in
the midst of the spell. Magical silence or physical gagging will prevent
verbal (V) spell completion. Magical immobility prevents any spell
casting. Physical restraint, including grappling, grasping, binding, etc.
prevents proper somatic (S)spell completion, for gestures must be exact
and movements free and as prescribed. Despite these restrictions, there is
no doubt that spells in general are potent offensive and defensive
weapons, providing the caster does not hesitate, i.e. he or she must know
which spell is being cast when the melee round begins.
Note that this is purely descriptive, but does contain an example of being hit and thus damaged and unable to finish the spell.
1EPHB104 said:Unless combat is spell versus spell, many such attacks will happen near the
end of a melee round. This is because the spell requires a relatively
lengthy time to cast, generally longer os spell level increases, so high
level spells may take over a full melee round to cast. Furthermore, if the
spell caster is struck, grabbed, or mogicolly attacked (and fails to make the
requisite saving throw - explained later), the spell will be spoiled and
fail. Spell combat includes cleric and magic-user, as well as monster-
oriented spells. Curative spells are handled likewise.
Reiteration of the same points, with a bit more precision. Notice how in THIS case a save is mentioned and the criteria is spelled out as 'struck, grabbed, or magically attacked'. Of course this may not be ALL possible conditions, so now, we can go on to the DMG
Page 65 of the 1e DMG contains the RULES for spell casting in melee (labeled as such). They specify the concrete things that will actually prevent or spoil spell casting. As far as enemy action goes the only things specified is that the caster cannot be HIT by an attack or fail a save during casting. It is quite clear that it is POSSIBLE to cast spells in melee, otherwise why would the section even be labeled 'casting spells in melee combat'?
There's no ambiguity at all whatsoever. In 1e (and I could dig up the corresponding rules for 2e but it is redundant) you CAN cast spells while being meleed. You cannot gain your dex bonus and your spell is spoiled if you are hit, that's it. Now, presumably pushing someone requires some sort of hit. 1e doesn't have a rule for that actually, so we're left to our own devices there, at least until 2e, which does have such rules.