Shell: Fix job control and backgrounding

This patchset makes the shell capable of lazily resolving and executing
sequences of commands, to allow for putting logical sequences in the
background.
In particular, it enables And/Or/Sequence nodes to be run in the background,
and consequently unmarks them as `would_execute`.
Doing so also fixes job control to an extent, as jobs are now capable of
having 'tails', so sequences can be put in the background while
preserving their following sequences.

Shell/AST.cpp

@@ -184,22 +184,9 @@ void And::dump(int level) const
 
 RefPtr<Value> And::run(RefPtr<Shell> shell)
 {
-    auto left = m_left->run(shell);
-    ASSERT(left->is_job());
-
-    auto* job_value = static_cast<JobValue*>(left.ptr());
-    const auto job = job_value->job();
-    if (!job) {
-        // Something has gone wrong, let's just pretend that the job failed.
-        return job_value;
-    }
-
-    shell->block_on_job(job);
-
-    if (job->exit_code() == 0)
-        return m_right->run(shell);
-
-    return job_value;
+    auto commands = m_left->run(shell)->resolve_as_commands(shell);
+    commands.last().next_chain.append(NodeWithAction { *m_right, NodeWithAction::And });
+    return create<CommandSequenceValue>(move(commands));
 }
 
 void And::highlight_in_editor(Line::Editor& editor, Shell& shell, HighlightMetadata metadata)
@@ -354,16 +341,11 @@ RefPtr<Value> Background::run(RefPtr<Shell> shell)
     //        all but their last subnode before yielding to this, causing a command
     //        like `foo && bar&` to effectively be `foo && (bar&)`.
     auto value = m_command->run(shell)->resolve_without_cast(shell);
-    if (value->is_job()) {
-        auto job = static_cast<JobValue*>(value.ptr())->job();
-        job->set_running_in_background(true);
-        job->set_should_announce_exit(true);
-        return value;
-    }
+    ASSERT(!value->is_job());
 
     auto commands = value->resolve_as_commands(shell);
-    auto& last = commands.last();
-    last.should_wait = false;
+    for (auto& command : commands)
+        command.should_wait = false;
 
     return create<CommandSequenceValue>(move(commands));
 }
@@ -925,7 +907,7 @@ void Execute::for_each_entry(RefPtr<Shell> shell, Function<IterationDecision(Ref
         }
         auto& last_in_commands = commands.last();
 
-        last_in_commands.redirections.append(FdRedirection::create(STDOUT_FILENO, pipefd[1], Rewiring::Close::Destination));
+        last_in_commands.redirections.prepend(FdRedirection::create(STDOUT_FILENO, pipefd[1], Rewiring::Close::Destination));
         last_in_commands.should_wait = false;
         last_in_commands.should_notify_if_in_background = false;
         last_in_commands.is_pipe_source = false;
@@ -1042,16 +1024,10 @@ void Execute::for_each_entry(RefPtr<Shell> shell, Function<IterationDecision(Ref
         return;
     }
 
-    RefPtr<Job> last_job;
-
-    for (auto& job : shell->run_commands(commands)) {
-        shell->block_on_job(job);
-        last_job = move(job);
-    }
-
-    callback(create<JobValue>(move(last_job)));
+    auto jobs = shell->run_commands(commands);
 
-    return;
+    if (!jobs.is_empty())
+        callback(create<JobValue>(&jobs.last()));
 }
 
 RefPtr<Value> Execute::run(RefPtr<Shell> shell)
@@ -1150,7 +1126,7 @@ RefPtr<Value> IfCond::run(RefPtr<Shell> shell)
     if (cond_job->signaled())
         return create<ListValue>({}); // Exit early.
 
-    if (cond_job->exit_code() == 0) {
+    if (shell->last_return_code == 0) {
         if (m_true_branch)
             return m_true_branch->run(shell);
     } else {
@@ -1287,23 +1263,9 @@ void Or::dump(int level) const
 
 RefPtr<Value> Or::run(RefPtr<Shell> shell)
 {
-
-    auto left = m_left->run(shell);
-    ASSERT(left->is_job());
-
-    auto* job_value = static_cast<JobValue*>(left.ptr());
-    const auto job = job_value->job();
-    if (!job) {
-        // Something has gone wrong, let's just pretend that the job failed.
-        return m_right->run(shell);
-    }
-
-    shell->block_on_job(job);
-
-    if (job->exit_code() == 0)
-        return job_value;
-
-    return m_right->run(shell);
+    auto commands = m_left->run(shell)->resolve_as_commands(shell);
+    commands.last().next_chain.empend(*m_right, NodeWithAction::Or);
+    return create<CommandSequenceValue>(move(commands));
 }
 
 void Or::highlight_in_editor(Line::Editor& editor, Shell& shell, HighlightMetadata metadata)
@@ -1549,6 +1511,7 @@ RefPtr<Value> Sequence::run(RefPtr<Shell> shell)
         execute_node = create<AST::Execute>(m_right->position(), m_right);
         return execute_node->run(shell);
     }
+
     auto left = m_left->run(shell)->resolve_as_commands(shell);
     // This could happen if a comment is next to a command.
     if (left.size() == 1) {
@@ -1557,13 +1520,12 @@ RefPtr<Value> Sequence::run(RefPtr<Shell> shell)
             return m_right->run(shell);
     }
 
-    auto right = m_right->run(shell)->resolve_as_commands(shell);
-
-    Vector<Command> commands;
-    commands.append(left);
-    commands.append(right);
+    if (left.last().should_wait)
+        left.last().next_chain.append(NodeWithAction { *m_right, NodeWithAction::Sequence });
+    else
+        left.append(m_right->run(shell)->resolve_as_commands(shell));
 
-    return create<CommandSequenceValue>(move(commands));
+    return create<CommandSequenceValue>(move(left));
 }
 
 void Sequence::highlight_in_editor(Line::Editor& editor, Shell& shell, HighlightMetadata metadata)

Shell/AST.h

@@ -28,6 +28,7 @@
 
 #include "Forward.h"
 #include "Job.h"
+#include <AK/InlineLinkedList.h>
 #include <AK/NonnullRefPtr.h>
 #include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
@@ -174,13 +175,30 @@ public:
     pid_t pgid { -1 };
 };
 
+struct NodeWithAction {
+    mutable NonnullRefPtr<Node> node;
+    enum Action {
+        And,
+        Or,
+        Sequence,
+    } action;
+
+    NodeWithAction(Node& node, Action action)
+        : node(node)
+        , action(action)
+    {
+    }
+};
+
 struct Command {
     Vector<String> argv;
     NonnullRefPtrVector<Redirection> redirections;
-    mutable RefPtr<Pipeline> pipeline;
     bool should_wait { true };
     bool is_pipe_source { false };
     bool should_notify_if_in_background { true };
+
+    mutable RefPtr<Pipeline> pipeline;
+    Vector<NodeWithAction> next_chain;
 };
 
 struct HitTestResult {
@@ -215,7 +233,7 @@ public:
     }
 
     CommandValue(Vector<String> argv)
-        : m_command({ move(argv), {}, {}, true, false, true })
+        : m_command({ move(argv), {}, true, false, true, nullptr, {} })
     {
     }
 
@@ -424,7 +442,6 @@ private:
     virtual void highlight_in_editor(Line::Editor&, Shell&, HighlightMetadata = {}) override;
     virtual HitTestResult hit_test_position(size_t) override;
     virtual String class_name() const override { return "And"; }
-    virtual bool would_execute() const override { return true; }
 
     RefPtr<Node> m_left;
     RefPtr<Node> m_right;
@@ -458,7 +475,6 @@ private:
     virtual void highlight_in_editor(Line::Editor&, Shell&, HighlightMetadata = {}) override;
     virtual HitTestResult hit_test_position(size_t) override;
     virtual String class_name() const override { return "Background"; }
-    virtual bool would_execute() const override { return m_command->would_execute(); }
 
     RefPtr<Node> m_command;
 };
@@ -725,7 +741,6 @@ private:
     virtual void highlight_in_editor(Line::Editor&, Shell&, HighlightMetadata = {}) override;
     virtual HitTestResult hit_test_position(size_t) override;
     virtual String class_name() const override { return "Or"; }
-    virtual bool would_execute() const override { return true; }
 
     RefPtr<Node> m_left;
     RefPtr<Node> m_right;

Shell/Forward.h

@@ -29,10 +29,11 @@
 class Shell;
 namespace AST {
 
+struct Command;
 class Node;
 class Value;
 class SyntaxError;
 class Pipeline;
-class Rewiring;
+struct Rewiring;
 
 }

Shell/Job.cpp

@@ -26,6 +26,7 @@
 
 #include "Job.h"
 #include "AST.h"
+#include "Shell.h"
 #include <inttypes.h>
 #include <stdio.h>
 #include <sys/wait.h>
@@ -70,3 +71,42 @@ bool Job::print_status(PrintStatusMode mode)
 
     return true;
 }
+
+Job::Job(pid_t pid, unsigned pgid, String cmd, u64 job_id, AST::Command&& command)
+    : m_pgid(pgid)
+    , m_pid(pid)
+    , m_job_id(job_id)
+    , m_cmd(move(cmd))
+{
+    m_command = make<AST::Command>(move(command));
+
+    set_running_in_background(false);
+    m_command_timer.start();
+}
+
+void Job::set_has_exit(int exit_code)
+{
+    if (m_exited)
+        return;
+    m_exit_code = exit_code;
+    m_exited = true;
+    if (on_exit)
+        on_exit(*this);
+}
+
+void Job::set_signalled(int sig)
+{
+    if (m_exited)
+        return;
+    m_exited = true;
+    m_exit_code = 126;
+    m_term_sig = sig;
+    if (on_exit)
+        on_exit(*this);
+}
+
+void Job::unblock() const
+{
+    if (!m_exited && on_exit)
+        on_exit(*this);
+}

Shell/Job.h

@@ -41,9 +41,11 @@
 #    undef JOB_TIME_INFO
 #endif
 
+struct LocalFrame;
+
 class Job : public RefCounted<Job> {
 public:
-    static NonnullRefPtr<Job> create(pid_t pid, pid_t pgid, String command, u64 job_id, AST::Pipeline* pipeline = nullptr) { return adopt(*new Job(pid, pgid, move(command), job_id, pipeline)); }
+    static NonnullRefPtr<Job> create(pid_t pid, pid_t pgid, String cmd, u64 job_id, AST::Command&& command) { return adopt(*new Job(pid, pgid, move(cmd), job_id, move(command))); }
 
     ~Job()
     {
@@ -53,13 +55,15 @@ public:
             dbg() << "Command \"" << m_cmd << "\" finished in " << elapsed << " ms";
         }
 #endif
-        if (m_pipeline)
-            m_pipeline = nullptr;
     }
 
+    Function<void(RefPtr<Job>)> on_exit;
+
     pid_t pgid() const { return m_pgid; }
     pid_t pid() const { return m_pid; }
     const String& cmd() const { return m_cmd; }
+    const AST::Command& command() const { return *m_command; }
+    AST::Command* command_ptr() { return m_command; }
     u64 job_id() const { return m_job_id; }
     bool exited() const { return m_exited; }
     bool signaled() const { return m_term_sig != -1; }
@@ -78,34 +82,12 @@ public:
     bool is_running_in_background() const { return m_running_in_background; }
     bool should_announce_exit() const { return m_should_announce_exit; }
     bool is_suspended() const { return m_is_suspended; }
-    void unblock() const
-    {
-        if (!m_exited && on_exit)
-            on_exit(*this);
-    }
-    Function<void(RefPtr<Job>)> on_exit;
+    void unblock() const;
 
     Core::ElapsedTimer& timer() { return m_command_timer; }
 
-    void set_has_exit(int exit_code)
-    {
-        if (m_exited)
-            return;
-        m_exit_code = exit_code;
-        m_exited = true;
-        if (on_exit)
-            on_exit(*this);
-    }
-    void set_signalled(int sig)
-    {
-        if (m_exited)
-            return;
-        m_exited = true;
-        m_exit_code = 126;
-        m_term_sig = sig;
-        if (on_exit)
-            on_exit(*this);
-    }
+    void set_has_exit(int exit_code);
+    void set_signalled(int sig);
 
     void set_is_suspended(bool value) const { m_is_suspended = value; }
 
@@ -127,18 +109,7 @@ public:
     bool print_status(PrintStatusMode);
 
 private:
-    Job(pid_t pid, unsigned pgid, String cmd, u64 job_id, AST::Pipeline* pipeline)
-        : m_pgid(pgid)
-        , m_pid(pid)
-        , m_job_id(job_id)
-        , m_cmd(move(cmd))
-    {
-        if (pipeline)
-            m_pipeline = *pipeline;
-
-        set_running_in_background(false);
-        m_command_timer.start();
-    }
+    Job(pid_t pid, unsigned pgid, String cmd, u64 job_id, AST::Command&& command);
 
     pid_t m_pgid { 0 };
     pid_t m_pid { 0 };
@@ -153,5 +124,5 @@ private:
     mutable bool m_active { true };
     mutable bool m_is_suspended { false };
     bool m_should_be_disowned { false };
-    RefPtr<AST::Pipeline> m_pipeline;
+    OwnPtr<AST::Command> m_command;
 };

Shell/Parser.cpp

@@ -283,7 +283,7 @@ RefPtr<AST::Node> Parser::parse_or_logical_sequence()
     if (!right_and_sequence)
         right_and_sequence = create<AST::SyntaxError>("Expected an expression after '||'");
 
-    return create<AST::Or>(create<AST::Execute>(move(and_sequence)), create<AST::Execute>(move(right_and_sequence)));
+    return create<AST::Or>(move(and_sequence), move(right_and_sequence));
 }
 
 RefPtr<AST::Node> Parser::parse_and_logical_sequence()
@@ -305,7 +305,7 @@ RefPtr<AST::Node> Parser::parse_and_logical_sequence()
     if (!right_and_sequence)
         right_and_sequence = create<AST::SyntaxError>("Expected an expression after '&&'");
 
-    return create<AST::And>(create<AST::Execute>(move(pipe_sequence)), create<AST::Execute>(move(right_and_sequence)));
+    return create<AST::And>(move(pipe_sequence), move(right_and_sequence));
 }
 
 RefPtr<AST::Node> Parser::parse_pipe_sequence()

Shell/Shell.cpp

@@ -421,15 +421,7 @@ int Shell::run_command(const StringView& cmd)
 
     tcgetattr(0, &termios);
 
-    auto result = command->run(*this);
-    if (result->is_job()) {
-        auto job_result = static_cast<AST::JobValue*>(result.ptr());
-        auto job = job_result->job();
-        if (!job)
-            last_return_code = 0;
-        else if (job->exited())
-            last_return_code = job->exit_code();
-    }
+    command->run(*this);
 
     return last_return_code;
 }
@@ -500,8 +492,11 @@ RefPtr<Job> Shell::run_command(const AST::Command& command)
     }
 
     int retval = 0;
-    if (run_builtin(command, rewirings, retval))
+    if (run_builtin(command, rewirings, retval)) {
+        for (auto& next_in_chain : command.next_chain)
+            run_tail(next_in_chain, retval);
         return nullptr;
+    }
 
     Vector<const char*> argv;
     Vector<String> copy_argv = command.argv;
@@ -619,15 +614,19 @@ RefPtr<Job> Shell::run_command(const AST::Command& command)
     StringBuilder cmd;
     cmd.join(" ", command.argv);
 
-    auto job = Job::create(child, pgid, cmd.build(), find_last_job_id() + 1, command.pipeline);
+    auto job = Job::create(child, pgid, cmd.build(), find_last_job_id() + 1, AST::Command(command));
     jobs.set((u64)child, job);
 
-    job->on_exit = [](auto job) {
+    job->on_exit = [this](auto job) {
         if (!job->exited())
             return;
         if (job->is_running_in_background() && job->should_announce_exit())
             fprintf(stderr, "Shell: Job %" PRIu64 "(%s) exited\n", job->job_id(), job->cmd().characters());
+
+        last_return_code = job->exit_code();
         job->disown();
+
+        run_tail(job);
     };
 
     fds.collect();
@@ -635,9 +634,42 @@ RefPtr<Job> Shell::run_command(const AST::Command& command)
     return *job;
 }
 
+void Shell::run_tail(const AST::NodeWithAction& next_in_chain, int head_exit_code)
+{
+    switch (next_in_chain.action) {
+    case AST::NodeWithAction::And:
+        if (head_exit_code == 0) {
+            auto commands = next_in_chain.node->run(*this)->resolve_as_commands(*this);
+            run_commands(commands);
+        }
+        break;
+    case AST::NodeWithAction::Or:
+        if (head_exit_code != 0) {
+            auto commands = next_in_chain.node->run(*this)->resolve_as_commands(*this);
+            run_commands(commands);
+        }
+        break;
+    case AST::NodeWithAction::Sequence:
+        auto commands = next_in_chain.node->run(*this)->resolve_as_commands(*this);
+        run_commands(commands);
+        break;
+    }
+}
+
+void Shell::run_tail(RefPtr<Job> job)
+{
+    if (auto cmd = job->command_ptr()) {
+        deferred_invoke([=, this](auto&) {
+            for (auto& next_in_chain : cmd->next_chain) {
+                run_tail(next_in_chain, job->exit_code());
+            }
+        });
+    }
+}
+
 NonnullRefPtrVector<Job> Shell::run_commands(Vector<AST::Command>& commands)
 {
-    NonnullRefPtrVector<Job> jobs_to_wait_for;
+    NonnullRefPtrVector<Job> spawned_jobs;
 
     for (auto& command : commands) {
 #ifdef SH_DEBUG
@@ -663,21 +695,19 @@ NonnullRefPtrVector<Job> Shell::run_commands(Vector<AST::Command>& commands)
         if (!job)
             continue;
 
+        spawned_jobs.append(*job);
         if (command.should_wait) {
             block_on_job(job);
-            if (!job->is_suspended())
-                jobs_to_wait_for.append(*job);
         } else {
             if (command.is_pipe_source) {
                 job->set_running_in_background(true);
-                jobs_to_wait_for.append(*job);
             } else if (command.should_notify_if_in_background) {
                 job->set_should_announce_exit(true);
             }
         }
     }
 
-    return jobs_to_wait_for;
+    return spawned_jobs;
 }
 
 bool Shell::run_file(const String& filename, bool explicitly_invoked)
@@ -709,6 +739,9 @@ void Shell::block_on_job(RefPtr<Job> job)
     if (!job)
         return;
 
+    if (job->is_suspended())
+        return; // We cannot wait for a suspended job.
+
     ScopeGuard io_restorer { [&]() {
         if (job->exited() && !job->is_running_in_background()) {
             restore_ios();

Shell/Shell.h

@@ -195,6 +195,9 @@ private:
     const Job* m_current_job { nullptr };
     LocalFrame* find_frame_containing_local_variable(const String& name);
 
+    void run_tail(RefPtr<Job>);
+    void run_tail(const AST::NodeWithAction&, int head_exit_code);
+
     virtual void custom_event(Core::CustomEvent&) override;
 
 #define __ENUMERATE_SHELL_BUILTIN(builtin) \

Shell/Tests/if.sh

@@ -1,13 +1,17 @@
 #!/bin/sh
 
+setopt --verbose
+
 if test 1 -eq 1 {
     # Are comments ok?
     # Basic 'if' structure, empty block.
     if true {
     } else {
+        echo "if true runs false branch"
         exit 2
     }
     if false {
+        echo "if false runs true branch"
         exit 2
     } else {
     }

Shell/Tests/valid.sh

@@ -23,69 +23,69 @@ test "$(echo yes)" = yes || exit 2
 alias fail="echo Failure: "
 
 # Redirections.
-test -z "$(echo foo > /dev/null)" || fail direct path redirection
-test -z "$(echo foo 2> /dev/null 1>&2)" || fail indirect redirection
-test -n "$(echo foo 2> /dev/null)" || fail fds interfere with each other
+test -z "$(echo foo > /dev/null)" || fail direct path redirection && exit 2
+test -z "$(echo foo 2> /dev/null 1>&2)" || fail indirect redirection && exit 2
+test -n "$(echo foo 2> /dev/null)" || fail fds interfere with each other && exit 2
 
 # Argument unpack
-test "$(echo (yes))" = yes || fail arguments inside bare lists
-test "$(echo (no)() yes)" = yes || fail arguments inside juxtaposition: empty
-test "$(echo (y)(es))" = yes || fail arguments inside juxtaposition: list
-test "$(echo "y"es)" = yes || fail arguments inside juxtaposition: string
+test "$(echo (yes))" = yes || fail arguments inside bare lists && exit 2
+test "$(echo (no)() yes)" = yes || fail arguments inside juxtaposition: empty && exit 2
+test "$(echo (y)(es))" = yes || fail arguments inside juxtaposition: list && exit 2
+test "$(echo "y"es)" = yes || fail arguments inside juxtaposition: string && exit 2
 
 # String substitution
 foo=yes
-test "$(echo $foo)" = yes || fail simple string var lookup
-test "$(echo "$foo")" = yes || fail stringified string var lookup
+test "$(echo $foo)" = yes || fail simple string var lookup && exit 2
+test "$(echo "$foo")" = yes || fail stringified string var lookup && exit 2
 
 # List substitution
 foo=(yes)
 # Static lookup, as list
-test "$(echo $foo)" = yes || fail simple list var lookup
+test "$(echo $foo)" = yes || fail simple list var lookup && exit 2
 # Static lookup, stringified
-test "$(echo "$foo")" = yes || fail stringified list var lookup
+test "$(echo "$foo")" = yes || fail stringified list var lookup && exit 2
 # Dynamic lookup through static expression
-test "$(echo $'foo')" = yes || fail dynamic lookup through static exp
+test "$(echo $'foo')" = yes || fail dynamic lookup through static exp && exit 2
 # Dynamic lookup through dynamic expression
 ref_to_foo=foo
-test "$(echo $"$ref_to_foo")" = yes || fail dynamic lookup through dynamic exp
+test "$(echo $"$ref_to_foo")" = yes || fail dynamic lookup through dynamic exp && exit 2
 
 # More redirections
 echo test > /tmp/sh-test
-test "$(cat /tmp/sh-test)" = test || fail simple path redirect
+test "$(cat /tmp/sh-test)" = test || fail simple path redirect && exit 2
 rm /tmp/sh-test
 
 # 'brace' expansions
-test "$(echo x(yes no))" = "xyes xno" || fail simple juxtaposition expansion
-test "$(echo (y n)(es o))" = "yes yo nes no" || fail list-list juxtaposition expansion
-test "$(echo ()(foo bar baz))" = "" || fail empty expansion
+test "$(echo x(yes no))" = "xyes xno" || fail simple juxtaposition expansion && exit 2
+test "$(echo (y n)(es o))" = "yes yo nes no" || fail list-list juxtaposition expansion && exit 2
+test "$(echo ()(foo bar baz))" = "" || fail empty expansion && exit 2
 
 # Variables inside commands
 to_devnull=(>/dev/null)
-test "$(echo hewwo $to_devnull)" = "" || fail variable containing simple command
+test "$(echo hewwo $to_devnull)" = "" || fail variable containing simple command && exit 2
 
 word_count=(() | wc -w)
-test "$(echo well hello friends $word_count)" -eq 3 || fail variable containing pipeline
+test "$(echo well hello friends $word_count)" -eq 3 || fail variable containing pipeline && exit 2
 
 # Globs
 mkdir sh-test
 pushd sh-test
     touch (a b c)(d e f)
-    test "$(echo a*)" = "ad ae af" || fail '*' glob expansion
-    test "$(echo a?)" = "ad ae af" || fail '?' glob expansion
+    test "$(echo a*)" = "ad ae af" || fail '*' glob expansion && exit 2
+    test "$(echo a?)" = "ad ae af" || fail '?' glob expansion && exit 2
 
     glob_in_var='*'
-    test "$(echo $glob_in_var)" = '*' || fail substituted string acts as glob
+    test "$(echo $glob_in_var)" = '*' || fail substituted string acts as glob && exit 2
 
-    test "$(echo (a*))" = "ad ae af" || fail globs in lists resolve wrong
-    test "$(echo x(a*))" = "xad xae xaf" || fail globs in lists do not resolve to lists
-    test "$(echo "foo"a*)" = "fooad fooae fooaf" || fail globs join to dquoted strings
+    test "$(echo (a*))" = "ad ae af" || fail globs in lists resolve wrong && exit 2
+    test "$(echo x(a*))" = "xad xae xaf" || fail globs in lists do not resolve to lists && exit 2
+    test "$(echo "foo"a*)" = "fooad fooae fooaf" || fail globs join to dquoted strings && exit 2
 popd
 rm -fr sh-test
 
 # Setopt
 setopt --inline_exec_keep_empty_segments
-test "$(echo -n "a\n\nb")" = "a  b" || fail inline_exec_keep_empty_segments has no effect
+test "$(echo -n "a\n\nb")" = "a  b" || fail inline_exec_keep_empty_segments has no effect && exit 2
 
 setopt --no_inline_exec_keep_empty_segments
-test "$(echo -n "a\n\nb")" = "a b" || fail cannot unset inline_exec_keep_empty_segments
+test "$(echo -n "a\n\nb")" = "a b" || fail cannot unset inline_exec_keep_empty_segments && exit 2