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Make while loops evaluate to the last executed command status

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A while loop now evaluates to the last executed command in the body, or
zero if the loop body is empty. This matches POSIX semantics.

Add a bunch of tricky tests.

See #4982
This commit is contained in:
ridiculousfish
2019-01-20 16:37:20 -08:00
parent fec10830d3
commit 1680b741b2
5 changed files with 88 additions and 21 deletions
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38
src/parse_execution.cpp
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@@ -524,13 +524,28 @@ parse_execution_result_t parse_execution_context_t::run_while_statement(
const block_t *associated_block) {
parse_execution_result_t ret = parse_execution_success;
// "The exit status of the while loop shall be the exit status of the last compound-list-2
// executed, or zero if none was executed."
// Here are more detailed requirements:
// - If we execute the loop body zero times, or the loop body is empty, the status is success.
// - An empty loop body is treated as true, both in the loop condition and after loop exit.
// - The exit status of the last command is visible in the loop condition. (i.e. do not set the
// exit status to true BEFORE executing the loop condition).
// We achieve this by restoring the status if the loop condition fails, plus a special
// affordance for the first condition.
bool first_cond_check = true;
// The conditions of the while loop.
tnode_t<g::job_conjunction> condition_head = header.child<1>();
tnode_t<g::andor_job_list> condition_boolean_tail = header.child<3>();
// Run while the condition is true.
bool loop_executed = false;
for (;;) {
// Save off the exit status if it came from the loop body. We'll restore it if the condition
// is false.
int cond_saved_status = first_cond_check ? EXIT_SUCCESS : proc_get_last_status();
first_cond_check = false;
// Check the condition.
parse_execution_result_t cond_ret =
this->run_job_conjunction(condition_head, associated_block);
@@ -538,8 +553,13 @@ parse_execution_result_t parse_execution_context_t::run_while_statement(
cond_ret = run_job_list(condition_boolean_tail, associated_block);
}
// We only continue on successful execution and EXIT_SUCCESS.
if (cond_ret != parse_execution_success || proc_get_last_status() != EXIT_SUCCESS) {
// If the loop condition failed to execute, then exit the loop without modifying the exit
// status. If the loop condition executed with a failure status, restore the status and then
// exit the loop.
if (cond_ret != parse_execution_success) {
break;
} else if (proc_get_last_status() != EXIT_SUCCESS) {
proc_set_last_status(cond_saved_status);
break;
}
@@ -549,8 +569,6 @@ parse_execution_result_t parse_execution_context_t::run_while_statement(
break;
}
loop_executed = true;
// Push a while block and then check its cancellation reason.
while_block_t *wb = parser->push_block<while_block_t>();
this->run_job_list(contents, wb);
@@ -573,16 +591,6 @@ parse_execution_result_t parse_execution_context_t::run_while_statement(
break;
}
}
// $status after `while` should be 0 if it executed at least once, otherwise the last `$status`
// obtained by executing the condition is preserved. See #4982.
if (loop_executed) {
// Do not override status if exiting due to the presence of an explict `return xxx` (#5513)
if (!associated_block->skip) {
proc_set_last_status(STATUS_CMD_OK);
}
}
return ret;
}