Thread pgroups into command substitutions

Give string expansion an (optional) parent pgroup. This is threaded all
the way into eval(). This ensures that in a mixed pipeline like:

   cmd | begin ; something (cmd2) ; end

that cmd2 and cmd have the same pgroup.

Add a test to ensure that command substitutions inherit pgroups
properly.

cherry-pick of 938b683895

Fixes #6624

src/exec.cpp

@@ -1121,8 +1121,8 @@ bool exec_job(parser_t &parser, const shared_ptr<job_t> &j, const job_lineage_t
     return true;
 }
 
-static int exec_subshell_internal(const wcstring &cmd, parser_t &parser, wcstring_list_t *lst,
-                                  bool apply_exit_status, bool is_subcmd) {
+static int exec_subshell_internal(const wcstring &cmd, parser_t &parser, maybe_t<pid_t> parent_pgid,
+                                  wcstring_list_t *lst, bool apply_exit_status, bool is_subcmd) {
     ASSERT_IS_MAIN_THREAD();
     auto &ld = parser.libdata();
     bool prev_subshell = ld.is_subshell;
@@ -1144,7 +1144,8 @@ static int exec_subshell_internal(const wcstring &cmd, parser_t &parser, wcstrin
     // be null.
     std::shared_ptr<io_buffer_t> buffer;
     if (auto bufferfill = io_bufferfill_t::create(fd_set_t{}, ld.read_limit)) {
-        if (parser.eval(cmd, io_chain_t{bufferfill}, block_type_t::subst) == eval_result_t::ok) {
+        if (parser.eval(cmd, io_chain_t{bufferfill}, block_type_t::subst, parent_pgid) ==
+            eval_result_t::ok) {
             subcommand_statuses = parser.get_last_statuses();
         }
         buffer = io_bufferfill_t::finish(std::move(bufferfill));
@@ -1215,12 +1216,12 @@ static int exec_subshell_internal(const wcstring &cmd, parser_t &parser, wcstrin
 }
 
 int exec_subshell(const wcstring &cmd, parser_t &parser, wcstring_list_t &outputs,
-                  bool apply_exit_status, bool is_subcmd) {
+                  bool apply_exit_status, bool is_subcmd, maybe_t<pid_t> parent_pgid) {
     ASSERT_IS_MAIN_THREAD();
-    return exec_subshell_internal(cmd, parser, &outputs, apply_exit_status, is_subcmd);
+    return exec_subshell_internal(cmd, parser, parent_pgid, &outputs, apply_exit_status, is_subcmd);
 }
 
 int exec_subshell(const wcstring &cmd, parser_t &parser, bool apply_exit_status, bool is_subcmd) {
     ASSERT_IS_MAIN_THREAD();
-    return exec_subshell_internal(cmd, parser, nullptr, apply_exit_status, is_subcmd);
+    return exec_subshell_internal(cmd, parser, none(), nullptr, apply_exit_status, is_subcmd);
 }

src/exec.h

@@ -22,10 +22,12 @@ bool exec_job(parser_t &parser, const std::shared_ptr<job_t> &j, const job_linea
 ///
 /// \param cmd the command to execute
 /// \param outputs The list to insert output into.
+/// \param parent_pgid if set, the pgid for any spawned jobs
 ///
 /// \return the status of the last job to exit, or -1 if en error was encountered.
 int exec_subshell(const wcstring &cmd, parser_t &parser, wcstring_list_t &outputs,
-                  bool apply_exit_status, bool is_subcmd = false);
+                  bool apply_exit_status, bool is_subcmd = false,
+                  maybe_t<pid_t> parent_pgid = none());
 int exec_subshell(const wcstring &cmd, parser_t &parser, bool apply_exit_status,
                   bool is_subcmd = false);
 

src/expand.cpp

@@ -577,8 +577,9 @@ static expand_result_t expand_braces(const wcstring &instr, expand_flags_t flags
 }
 
 /// Perform cmdsubst expansion.
-static bool expand_cmdsubst(wcstring input, parser_t &parser, completion_list_t *out_list,
-                            parse_error_list_t *errors) {
+static bool expand_cmdsubst(wcstring input, const operation_context_t &ctx,
+                            completion_list_t *out_list, parse_error_list_t *errors) {
+    assert(ctx.parser && "Cannot expand without a parser");
     wchar_t *paren_begin = nullptr, *paren_end = nullptr;
     wchar_t *tail_begin = nullptr;
     size_t i, j;
@@ -605,14 +606,14 @@ static bool expand_cmdsubst(wcstring input, parser_t &parser, completion_list_t
 
     wcstring_list_t sub_res;
     const wcstring subcmd(paren_begin + 1, paren_end - paren_begin - 1);
-    if (exec_subshell(subcmd, parser, sub_res, true /* apply_exit_status */,
-                      true /* is_subcmd */) == -1) {
+    if (exec_subshell(subcmd, *ctx.parser, sub_res, true /* apply_exit_status */,
+                      true /* is_subcmd */, ctx.parent_pgid) == -1) {
         append_cmdsub_error(errors, SOURCE_LOCATION_UNKNOWN,
                             L"Unknown error while evaluating command substitution");
         return false;
     }
 
-    if (parser.get_last_status() == STATUS_READ_TOO_MUCH) {
+    if (ctx.parser->get_last_status() == STATUS_READ_TOO_MUCH) {
         append_cmdsub_error(
             errors, in - paren_begin,
             _(L"Too much data emitted by command substitution so it was discarded\n"));
@@ -652,7 +653,7 @@ static bool expand_cmdsubst(wcstring input, parser_t &parser, completion_list_t
     // Recursively call ourselves to expand any remaining command substitutions. The result of this
     // recursive call using the tail of the string is inserted into the tail_expand array list
     completion_list_t tail_expand;
-    expand_cmdsubst(tail_begin, parser, &tail_expand, errors);  // TODO: offset error locations
+    expand_cmdsubst(tail_begin, ctx, &tail_expand, errors);  // TODO: offset error locations
 
     // Combine the result of the current command substitution with the result of the recursive tail
     // expansion.
@@ -686,7 +687,7 @@ static bool expand_cmdsubst(wcstring input, parser_t &parser, completion_list_t
         }
     }
 
-    return parser.get_last_status() != STATUS_READ_TOO_MUCH;
+    return ctx.parser->get_last_status() != STATUS_READ_TOO_MUCH;
 }
 
 // Given that input[0] is HOME_DIRECTORY or tilde (ugh), return the user's name. Return the empty
@@ -897,7 +898,7 @@ expand_result_t expander_t::stage_cmdsubst(wcstring input, completion_list_t *ou
         }
     } else {
         assert(ctx.parser && "Must have a parser to expand command substitutions");
-        bool cmdsubst_ok = expand_cmdsubst(std::move(input), *ctx.parser, out, errors);
+        bool cmdsubst_ok = expand_cmdsubst(std::move(input), ctx, out, errors);
         if (!cmdsubst_ok) return expand_result_t::error;
     }
 

src/operation_context.h

@@ -29,6 +29,11 @@ class operation_context_t {
     // context itself.
     const environment_t &vars;
 
+    /// The pgid of the parental job.
+    /// This is used only when expanding command substitutions. If this is set, any jobs created by
+    /// the command substitions should use this pgid.
+    maybe_t<pid_t> parent_pgid{};
+
     // A function which may be used to poll for cancellation.
     cancel_checker_t cancel_checker;
 

src/parser.cpp

@@ -634,11 +634,11 @@ profile_item_t *parser_t::create_profile_item() {
 }
 
 eval_result_t parser_t::eval(const wcstring &cmd, const io_chain_t &io,
-                             enum block_type_t block_type) {
+                             enum block_type_t block_type, maybe_t<pid_t> parent_pgid) {
     // Parse the source into a tree, if we can.
     parse_error_list_t error_list;
     if (parsed_source_ref_t ps = parse_source(cmd, parse_flag_none, &error_list)) {
-        return this->eval(ps, io, block_type);
+        return this->eval(ps, io, block_type, parent_pgid);
     } else {
         // Get a backtrace. This includes the message.
         wcstring backtrace_and_desc;
@@ -651,11 +651,12 @@ eval_result_t parser_t::eval(const wcstring &cmd, const io_chain_t &io,
 }
 
 eval_result_t parser_t::eval(const parsed_source_ref_t &ps, const io_chain_t &io,
-                             enum block_type_t block_type) {
+                             enum block_type_t block_type, maybe_t<pid_t> parent_pgid) {
     assert(block_type == block_type_t::top || block_type == block_type_t::subst);
     if (!ps->tree.empty()) {
         job_lineage_t lineage;
         lineage.block_io = io;
+        lineage.parent_pgid = parent_pgid;
         // Execute the first node.
         tnode_t<grammar::job_list> start{&ps->tree, &ps->tree.front()};
         return this->eval_node(ps, start, std::move(lineage), block_type);
@@ -689,6 +690,9 @@ eval_result_t parser_t::eval_node(const parsed_source_ref_t &ps, tnode_t<T> node
     operation_context_t op_ctx = this->context();
     block_t *scope_block = this->push_block(block_t::scope_block(block_type));
 
+    // Propogate any parent pgid.
+    op_ctx.parent_pgid = lineage.parent_pgid;
+
     // Create and set a new execution context.
     using exc_ctx_ref_t = std::unique_ptr<parse_execution_context_t>;
     scoped_push<exc_ctx_ref_t> exc(&execution_context, make_unique<parse_execution_context_t>(

src/parser.h

@@ -266,15 +266,18 @@ class parser_t : public std::enable_shared_from_this<parser_t> {
     /// \param io io redirections to perform on all started jobs
     /// \param block_type The type of block to push on the block stack, which must be either 'top'
     /// or 'subst'.
+    /// \param parent_pgid if set, the pgid to give to spawned jobs
     ///
     /// \return the eval result,
     eval_result_t eval(const wcstring &cmd, const io_chain_t &io,
-                       block_type_t block_type = block_type_t::top);
+                       block_type_t block_type = block_type_t::top,
+                       maybe_t<pid_t> parent_pgid = {});
 
     /// Evaluate the parsed source ps.
     /// Because the source has been parsed, a syntax error is impossible.
     eval_result_t eval(const parsed_source_ref_t &ps, const io_chain_t &io,
-                       block_type_t block_type = block_type_t::top);
+                       block_type_t block_type = block_type_t::top,
+                       maybe_t<pid_t> parent_pgid = {});
 
     /// Evaluates a node.
     /// The node type must be grammar::statement or grammar::job_list.

tests/checks/pipeline-pgroup.fish

@@ -9,11 +9,13 @@ end
 # Here everything should live in the pgroup of the first fish_test_helper.
 $fth print_pgrp | read -g global_group | save_pgroup g1 | begin
     save_pgroup g2
+end | begin
+    echo (save_pgroup g3) >/dev/null
 end
 
-[ "$global_group" -eq "$g1" ] && [ "$g1" -eq "$g2" ]
+[ "$global_group" -eq "$g1" ] && [ "$g1" -eq "$g2" ] && [ "$g2" -eq "$g3" ]
 and echo "All pgroups agreed"
-or echo "Pgroups disagreed. Should be in $global_group but found $g1 and $g2"
+or echo "Pgroups disagreed. Should be in $global_group but found $g1, $g2, $g3"
 # CHECK: All pgroups agreed
 
 # Here everything should live in fish's pgroup.