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45111: zshmisc(1): Clarify the documentation of 'return' and 'exit' in conjunction with try/always

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Having reviewed 20076, 20084, 21734, and 21735, my understanding is that
the original intention was:

- A 'return' in a function does run always-list
- An 'exit' outside a function does not run always-list
- A 'return' outside a function is treated as an 'exit'

All of which are the case today.  The remaining case, of 'exit' used
inside a function, was not specified by the referenced -workers@ posts;
does, as implemented, run the always-list; and furthermore, based in
21734 it's fair to assume that the original documentation was assuming
that 'exit' would be used outside of any function, just like it assumed
'return' would be used inside a function.

Therefore, have the documentation specify only the behaviour of 'exit'
outside any function, and leave the behaviour of 'exit' inside
a function unspecified.  Anyone who relied on the documentation of 'exit'
as documented until this commit would have run into the
documentation/implementation discrepancy described in 45075.
This commit is contained in:
Daniel Shahaf 2019-12-21 12:41:03 +00:00
parent 105ca83aa2
commit a0c0aa41d2
5 changed files with 27 additions and 8 deletions
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16
Doc/Zsh/grammar.yo
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@ -297,11 +297,11 @@ findex(always)
cindex(always blocks)
cindex(try blocks)
item(tt({) var(try-list) tt(} always {) var(always-list) tt(}))(
First execute var(try-list). Regardless of errors, or tt(break),
tt(continue), or tt(return) commands encountered within var(try-list),
First execute var(try-list). Regardless of errors, or tt(break) or
tt(continue) commands encountered within var(try-list),
execute var(always-list). Execution then continues from the
result of the execution of var(try-list); in other words, any error,
or tt(break), tt(continue), or tt(return) command is treated in the
or tt(break) or tt(continue) command is treated in the
normal way, as if var(always-list) were not present. The two
chunks of code are referred to as the `try block' and the `always block'.
@ -345,10 +345,16 @@ example({
}
# The error condition has been reset.)
An tt(exit) command (or a tt(return) command executed at the outermost
function level of a script) encountered in tt(try-list) does em(not) cause
When a tt(try) block occurs outside of any function,
a tt(return) or a tt(exit) encountered in var(try-list) does em(not) cause
the execution of var(always-list). Instead, the shell exits immediately
after any tt(EXIT) trap has been executed.
Otherwise, a tt(return) command encountered in var(try-list) will cause the
execution of var(always-list), just like tt(break) and tt(continue).
COMMENT(The semantics of calling 'exit' in try-list inside a function are
deliberately left unspecified, because historically there was a mismatch between
the documented and implemented behaviours. Cf. 20076, 21734/21735, 45075.)
)
findex(function)
xitem(tt(function) var(word) ... [ tt(()) ] [ var(term) ] tt({) var(list) tt(}))