fish-shell/parse_execution.cpp

/**\file parse_execution.cpp

   Provides the "linkage" between a parse_node_tree_t and actual execution structures (job_t, etc.).

*/

#include "parse_execution.h"
#include "parse_util.h"
#include "complete.h"
#include "wildcard.h"
#include "builtin.h"
#include "parser.h"
#include "expand.h"
#include "wutil.h"
#include "exec.h"
#include "path.h"


parse_execution_context_t::parse_execution_context_t(const parse_node_tree_t &t, const wcstring &s, parser_t *p) : tree(t), src(s), parser(p), eval_level(0)
{
}

/* Utilities */

wcstring parse_execution_context_t::get_source(const parse_node_t &node) const
{
    return node.get_source(this->src);
}

const parse_node_t *parse_execution_context_t::get_child(const parse_node_t &parent, node_offset_t which, parse_token_type_t expected_type) const
{
    return this->tree.get_child(parent, which, expected_type);
}

node_offset_t parse_execution_context_t::get_offset(const parse_node_t &node) const
{
    /* Get the offset of a node via pointer arithmetic, very hackish */
    const parse_node_t *addr = &node;
    const parse_node_t *base = &this->tree.at(0);
    assert(addr >= base);
    node_offset_t offset = addr - base;
    assert(offset < this->tree.size());
    assert(&tree.at(offset) == &node);
    return offset;
}


bool parse_execution_context_t::should_cancel_execution(const block_t *block) const
{
    return block && (block->skip || block->loop_status != LOOP_NORMAL);
}

int parse_execution_context_t::run_if_statement(const parse_node_t &statement)
{
    assert(statement.type == symbol_if_statement);
    
    /* Push an if block */
    if_block_t *ib = new if_block_t();
    ib->node_offset = this->get_offset(statement);
    parser->push_block(ib);

    /* We have a sequence of if clauses, with a final else, resulting in a single job list that we execute */
    const parse_node_t *job_list_to_execute = NULL;
    const parse_node_t *if_clause = get_child(statement, 0, symbol_if_clause);
    const parse_node_t *else_clause = get_child(statement, 1, symbol_else_clause);
    while (! should_cancel_execution(ib))
    {
        assert(if_clause != NULL && else_clause != NULL);
        const parse_node_t &condition = *get_child(*if_clause, 1, symbol_job);
        if (run_1_job(condition, ib) == EXIT_SUCCESS)
        {
            /* condition succeeded */
            job_list_to_execute = get_child(*if_clause, 3, symbol_job_list);
            break;
        }
        else if (else_clause->child_count == 0)
        {
            /* 'if' condition failed, no else clause, we're done */
            job_list_to_execute = NULL;
            break;
        }
        else
        {
            /* We have an 'else continuation' (either else-if or else) */
            const parse_node_t &else_cont = *get_child(*else_clause, 1, symbol_else_continuation);
            assert(else_cont.production_idx < 2);
            if (else_cont.production_idx == 0)
            {
                /* it's an 'else if', go to the next one */
                if_clause = get_child(else_cont, 0, symbol_if_clause);
                else_clause = get_child(else_cont, 1, symbol_else_clause);
            }
            else
            {
                /* it's the final 'else', we're done */
                assert(else_cont.production_idx == 1);
                job_list_to_execute = get_child(else_cont, 1, symbol_job_list);
                break;
            }
        }
    }
    
    /* Execute any job list we got */
    if (job_list_to_execute != NULL)
    {
        run_job_list(*job_list_to_execute, ib);
    }

    /* Done */
    parser->pop_block(ib);
    
    return proc_get_last_status();
}

int parse_execution_context_t::run_begin_statement(const parse_node_t &header, const parse_node_t &contents)
{
    assert(header.type == symbol_begin_header);
    assert(contents.type == symbol_job_list);
    
    /* Basic begin/end block. Push a scope block. */
    scope_block_t *sb = new scope_block_t(BEGIN);
    parser->push_block(sb);
    
    /* Run the job list */
    run_job_list(contents, sb);
    
    /* Pop the block */
    parser->pop_block(sb);
    
    return proc_get_last_status();
}

/* Define a function */
int parse_execution_context_t::run_function_statement(const parse_node_t &header, const parse_node_t &contents)
{
    assert(header.type == symbol_function_header);
    assert(contents.type == symbol_job_list);
    
    /* Get arguments */
    const parse_node_t *unmatched_wildcard = NULL;
    wcstring_list_t argument_list = this->determine_arguments(header, &unmatched_wildcard);
    
    bool errored = false;
    if (unmatched_wildcard != NULL)
    {
        errored = append_unmatched_wildcard_error(*unmatched_wildcard);
    }
    
    if (! errored)
    {
        const wcstring contents_str = get_source(contents);
        wcstring error_str;
        int err = define_function(*parser, argument_list, contents_str, &error_str);
        proc_set_last_status(err);
        
        if (! error_str.empty())
        {
            this->append_error(header, L"%ls", error_str.c_str());
        }
    }
    return proc_get_last_status();
}

int parse_execution_context_t::run_block_statement(const parse_node_t &statement)
{
    assert(statement.type == symbol_block_statement);
    
    const parse_node_t &block_header = *get_child(statement, 0, symbol_block_header); //block header
    const parse_node_t &header = *get_child(block_header, 0); //specific header type (e.g. for loop)
    const parse_node_t &contents = *get_child(statement, 2, symbol_job_list); //block contents
    
    int ret = 1;
    switch (header.type)
    {
        case symbol_for_header:
            ret = run_for_statement(header, contents);
            break;
            
        case symbol_while_header:
            ret = run_while_statement(header, contents);
            break;
            
        case symbol_function_header:
            ret = run_function_statement(header, contents);
            break;
            
        case symbol_begin_header:
            ret = run_begin_statement(header, contents);
            break;
        
        default:
            fprintf(stderr, "Unexpected block header: %ls\n", header.describe().c_str());
            PARSER_DIE();
            break;
    }
    
    return proc_get_last_status();
}

int parse_execution_context_t::run_for_statement(const parse_node_t &header, const parse_node_t &block_contents)
{
    assert(header.type == symbol_for_header);
    assert(block_contents.type == symbol_job_list);
    
    /* Get the variable name: `for var_name in ...` */
    const parse_node_t &var_name_node = *get_child(header, 1, parse_token_type_string);
    const wcstring for_var_name = get_source(var_name_node);
    
    /* Get the contents to iterate over. Here we could do something with unmatched_wildcard. However it seems nicer to not make for loops complain about this, i.e. just iterate over a potentially empty list
    */
    wcstring_list_t argument_list = this->determine_arguments(header, NULL);
    
    for_block_t *fb = new for_block_t(for_var_name);
    parser->push_block(fb);

    /* Note that we store the sequence of values in opposite order */
    std::reverse(argument_list.begin(), argument_list.end());
    fb->sequence = argument_list;

    /* Now drive the for loop. TODO: handle break, etc. */
    while (! fb->sequence.empty() && ! should_cancel_execution(fb))
    {
        const wcstring &for_variable = fb->variable;
        const wcstring &val = fb->sequence.back();
        env_set(for_variable, val.c_str(),  ENV_LOCAL);
        fb->sequence.pop_back();
        fb->loop_status = LOOP_NORMAL;
        fb->skip = 0;
        
        this->run_job_list(block_contents, fb);
        
        /* Handle break or continue */
        if (fb->loop_status == LOOP_CONTINUE)
        {
            /* Reset the loop state */
            fb->loop_status = LOOP_NORMAL;
            fb->skip = false;
            continue;
        }
        else if (fb->loop_status == LOOP_BREAK)
        {
            break;
        }
    }
    
    return proc_get_last_status();
}


int parse_execution_context_t::run_switch_statement(const parse_node_t &statement)
{
    assert(statement.type == symbol_switch_statement);
    bool errored = false;
    const parse_node_t *matching_case_item = NULL;
    
    /* Get the switch variable */
    const parse_node_t &switch_value_node = *get_child(statement, 1, parse_token_type_string);
    const wcstring switch_value = get_source(switch_value_node);
    
    /* Expand it */
    std::vector<completion_t> switch_values_expanded;
    int expand_ret = expand_string(switch_value, switch_values_expanded, EXPAND_NO_DESCRIPTIONS);
    switch (expand_ret)
    {
        case EXPAND_ERROR:
        {
            errored = append_error(switch_value_node,
                  _(L"Could not expand string '%ls'"),
                  switch_value.c_str());
            break;
        }
            
        case EXPAND_WILDCARD_NO_MATCH:
        {
            /* Store the node that failed to expand */
            errored = append_error(switch_value_node, WILDCARD_ERR_MSG, switch_value.c_str());
            break;
        }
        
        case EXPAND_WILDCARD_MATCH:
        case EXPAND_OK:
        {
            break;
        }
    }
    
    if (! errored && switch_values_expanded.size() != 1)
    {
            errored = append_error(switch_value_node,
                _(L"switch: Expected exactly one argument, got %lu\n"),
                switch_values_expanded.size());
    }
    const wcstring &switch_value_expanded = switch_values_expanded.at(0).completion;
    
    switch_block_t *sb = new switch_block_t(switch_value_expanded);
    parser->push_block(sb);
    
    if (! errored)
    {
        /* Expand case statements */
        const parse_node_t *case_item_list = get_child(statement, 3, symbol_case_item_list);
        while (matching_case_item == NULL && case_item_list->child_count > 0 && ! should_cancel_execution(sb))
        {
            if (case_item_list->production_idx == 2)
            {
                /* Hackish: blank line */
                case_item_list = get_child(*case_item_list, 1, symbol_case_item_list);
                continue;
            }
            
            /* Pull out this case item and the rest of the list */
            const parse_node_t &case_item = *get_child(*case_item_list, 0, symbol_case_item);
            
            /* Pull out the argument list */
            const parse_node_t &arg_list = *get_child(case_item, 1, symbol_argument_list);
            
            /* Expand arguments. We explicitly ignore unmatched_wildcard. That is, a case item list may have a wildcard that fails to expand to anything. */
            const wcstring_list_t case_args = this->determine_arguments(arg_list, NULL);
            
            for (size_t i=0; i < case_args.size(); i++)
            {
                const wcstring &arg = case_args.at(i);
                
                /* Unescape wildcards so they can be expanded again */
                wchar_t *unescaped_arg = parse_util_unescape_wildcards(arg.c_str());
                bool match = wildcard_match(switch_value_expanded, unescaped_arg);
                free(unescaped_arg);
                
                /* If this matched, we're done */
                if (match)
                {
                    matching_case_item = &case_item;
                    break;
                }
            }
            
            /* Remainder of the list */
            case_item_list = get_child(*case_item_list, 1, symbol_case_item_list);
        }
    }
    
    if (! errored && matching_case_item)
    {
        /* Success, evaluate the job list */
        const parse_node_t *job_list = get_child(*matching_case_item, 3, symbol_job_list);
        this->run_job_list(*job_list, sb);
    }

    parser->pop_block(sb);

    // Oops, this is stomping STATUS_WILDCARD_ERROR. TODO: Don't!
    if (errored)
        proc_set_last_status(STATUS_BUILTIN_ERROR);
    return proc_get_last_status();
}

int parse_execution_context_t::run_while_statement(const parse_node_t &header, const parse_node_t &block_contents)
{
    assert(header.type == symbol_while_header);
    assert(block_contents.type == symbol_job_list);
    
    /* Push a while block */
    while_block_t *wb = new while_block_t();
    wb->status = WHILE_TEST_FIRST;
    wb->node_offset = this->get_offset(header);
    parser->push_block(wb);
    
    /* The condition and contents of the while loop, as a job and job list respectively */
    const parse_node_t &while_condition = *get_child(header, 1, symbol_job);
    
    /* A while loop is a while loop! */
    while (! this->should_cancel_execution(wb) && this->run_1_job(while_condition, wb) == EXIT_SUCCESS)
    {
        /* The block ought to go inside the loop (see #1212) */
        this->run_job_list(block_contents, wb);
        
        /* Handle break or continue */
        if (wb->loop_status == LOOP_CONTINUE)
        {
            /* Reset the loop state */
            wb->loop_status = LOOP_NORMAL;
            wb->skip = false;
            continue;
        }
        else if (wb->loop_status == LOOP_BREAK)
        {
            break;
        }
    }
    
    /* Done */
    parser->pop_block(wb);
    
    return proc_get_last_status();
}

/* Appends an error to the error list. Always returns true, so you can assign the result to an 'errored' variable */
bool parse_execution_context_t::append_error(const parse_node_t &node, const wchar_t *fmt, ...)
{
    parse_error_t error;
    error.source_start = node.source_start;
    error.source_length = node.source_length;
    error.code = parse_error_syntax; //hackish
    
    va_list va;
    va_start(va, fmt);
    error.text = vformat_string(fmt, va);
    va_end(va);
    
    this->errors.push_back(error);
    return true;
}

/* Appends an unmatched wildcard error to the error list, and returns true. */
bool parse_execution_context_t::append_unmatched_wildcard_error(const parse_node_t &unmatched_wildcard)
{
    proc_set_last_status(STATUS_UNMATCHED_WILDCARD);
    return append_error(unmatched_wildcard, WILDCARD_ERR_MSG, get_source(unmatched_wildcard).c_str());
}



/* Creates a 'normal' (non-block) process */
process_t *parse_execution_context_t::create_plain_process(job_t *job, const parse_node_t &statement)
{
    bool errored = false;
    
    /* Get the decoration */
    assert(statement.type == symbol_plain_statement);
    
    /* Get the command. We expect to always get it here. */
    wcstring cmd;
    bool got_cmd = tree.command_for_plain_statement(statement, src, &cmd);
    assert(got_cmd);
    
    /* Expand it as a command. Return NULL on failure. */
    bool expanded = expand_one(cmd, EXPAND_SKIP_CMDSUBST | EXPAND_SKIP_VARIABLES);
    if (! expanded)
    {
        errored = append_error(statement, ILLEGAL_CMD_ERR_MSG, cmd.c_str());
    }
    
    if (errored)
        return NULL;
    
    /* The list of arguments. The command is the first argument. TODO: count hack */
    const parse_node_t *unmatched_wildcard = NULL;
    wcstring_list_t argument_list = this->determine_arguments(statement, &unmatched_wildcard);
    argument_list.insert(argument_list.begin(), cmd);
    
    /* If we were not able to expand any wildcards, here is the first one that failed */
    if (unmatched_wildcard != NULL)
    {
        job_set_flag(job, JOB_WILDCARD_ERROR, 1);
        errored = append_unmatched_wildcard_error(*unmatched_wildcard);
    }
    
    if (errored)
        return NULL;
    
    /* The set of IO redirections that we construct for the process */
    io_chain_t process_io_chain;
    errored = ! this->determine_io_chain(statement, &process_io_chain);
    if (errored)
        return NULL;
    
    /* Determine the process type, which depends on the statement decoration (command, builtin, etc) */
    enum parse_statement_decoration_t decoration = tree.decoration_for_plain_statement(statement);
    enum process_type_t process_type = EXTERNAL;
    
    /* exec hack */
    if (decoration != parse_statement_decoration_command && cmd == L"exec")
    {
        /* Either 'builtin exec' or just plain 'exec', and definitely not 'command exec'. Note we don't allow overriding exec with a function. */
        process_type = INTERNAL_EXEC;
    }
    else if (decoration == parse_statement_decoration_command)
    {
        /* Always a command */
        process_type = EXTERNAL;
    }
    else if (decoration == parse_statement_decoration_builtin)
    {
        /* What happens if this builtin is not valid? */
        process_type = INTERNAL_BUILTIN;
    }
    else if (function_exists(cmd))
    {
        process_type = INTERNAL_FUNCTION;
    }
    else if (builtin_exists(cmd))
    {
        process_type = INTERNAL_BUILTIN;
    }
    else
    {
        process_type = EXTERNAL;
    }
    
    wcstring actual_cmd;
    if (process_type == EXTERNAL)
    {
        /* Determine the actual command. Need to support implicit cd here */
        bool has_command = path_get_path(cmd, &actual_cmd);
        
        if (! has_command)
        {
            /* TODO: support fish_command_not_found, implicit cd, etc. here */
            errored = true;
        }
    }
    
    /* Return the process, or NULL on error */
    process_t *result = NULL;
    if (! errored)
    {
        result = new process_t();
        result->type = process_type;
        result->set_argv(argument_list);
        result->set_io_chain(process_io_chain);
        result->actual_cmd = actual_cmd;
    }
    return result;
}

/* Determine the list of arguments, expanding stuff. If we have a wildcard and none could be expanded, return the unexpandable wildcard node by reference. */
wcstring_list_t parse_execution_context_t::determine_arguments(const parse_node_t &parent, const parse_node_t **out_unmatched_wildcard_node)
{
    wcstring_list_t argument_list;
    
    /* Whether we failed to match any wildcards, and succeeded in matching any wildcards */
    bool unmatched_wildcard = false, matched_wildcard = false;
    
    /* First node that failed to expand as a wildcard (if any) */
    const parse_node_t *unmatched_wildcard_node = NULL;
    
    /* Get all argument nodes underneath the statement */
    const parse_node_tree_t::parse_node_list_t argument_nodes = tree.find_nodes(parent, symbol_argument);
    argument_list.reserve(argument_nodes.size());
    for (size_t i=0; i < argument_nodes.size(); i++)
    {
        const parse_node_t &arg_node = *argument_nodes.at(i);
        
        /* Expect all arguments to have source */
        assert(arg_node.has_source());
        const wcstring arg_str = arg_node.get_source(src);
        
        /* Expand this string */
        std::vector<completion_t> arg_expanded;
        int expand_ret = expand_string(arg_str, arg_expanded, EXPAND_NO_DESCRIPTIONS);
        switch (expand_ret)
        {
            case EXPAND_ERROR:
            {
                this->append_error(arg_node,
                      _(L"Could not expand string '%ls'"),
                      arg_str.c_str());
                break;
            }
                
            case EXPAND_WILDCARD_NO_MATCH:
            {
                /* Store the node that failed to expand */
                unmatched_wildcard = true;
                if (! unmatched_wildcard_node)
                {
                    unmatched_wildcard_node = &arg_node;
                }
                break;
            }
            
            case EXPAND_WILDCARD_MATCH:
            {
                matched_wildcard = true;
                break;
            }
            
            case EXPAND_OK:
            {
                break;
            }
        }
        
        /* Now copy over any expanded arguments */
        for (size_t i=0; i < arg_expanded.size(); i++)
        {
            argument_list.push_back(arg_expanded.at(i).completion);
        }
    }
    
    /* Return if we had a wildcard problem */
    if (out_unmatched_wildcard_node != NULL && unmatched_wildcard && ! matched_wildcard)
    {
        *out_unmatched_wildcard_node = unmatched_wildcard_node;
    }
    
    return argument_list;
}

bool parse_execution_context_t::determine_io_chain(const parse_node_t &statement_node, io_chain_t *out_chain)
{
    io_chain_t result;
    bool errored = false;
    
    /* We are called with a statement of varying types. We require that the statement have an arguments_or_redirections_list child. */
    const parse_node_t &args_and_redirections_list = tree.find_child(statement_node, symbol_arguments_or_redirections_list);
    
    /* Get all redirection nodes underneath the statement */
    const parse_node_tree_t::parse_node_list_t redirect_nodes = tree.find_nodes(args_and_redirections_list, symbol_redirection);
    for (size_t i=0; i < redirect_nodes.size(); i++)
    {
        const parse_node_t &redirect_node = *redirect_nodes.at(i);
        
        int source_fd = -1; /* source fd */
        wcstring target; /* file path or target fd */
        enum token_type redirect_type = tree.type_for_redirection(redirect_node, src, &source_fd, &target);
        
        /* PCA: I can't justify this EXPAND_SKIP_VARIABLES flag. It was like this when I got here. */
        bool target_expanded = expand_one(target, no_exec ? EXPAND_SKIP_VARIABLES : 0);
        if (! target_expanded || target.empty())
        {
            /* Should improve this error message */
            errored = append_error(redirect_node,
                  _(L"Invalid redirection target: %ls"),
                  target.c_str());
        }
        
        
        /* Generate the actual IO redirection */
        shared_ptr<io_data_t> new_io;
        assert(redirect_type != TOK_NONE);
        switch (redirect_type)
        {
            case TOK_REDIRECT_FD:
            {
                if (target == L"-")
                {
                    new_io.reset(new io_close_t(source_fd));
                }
                else
                {
                    wchar_t *end = NULL;
                    errno = 0;
                    int old_fd = fish_wcstoi(target.c_str(), &end, 10);
                    if (old_fd < 0 || errno || *end)
                    {
                        errored = append_error(redirect_node,
                              _(L"Requested redirection to something that is not a file descriptor %ls"),
                              target.c_str());
                    }
                    else
                    {
                        new_io.reset(new io_fd_t(source_fd, old_fd));
                    }
                }
                break;
            }
            
            case TOK_REDIRECT_OUT:
            case TOK_REDIRECT_APPEND:
            case TOK_REDIRECT_IN:
            case TOK_REDIRECT_NOCLOB:
            {
                int oflags = oflags_for_redirection_type(redirect_type);
                io_file_t *new_io_file = new io_file_t(source_fd, target, oflags);
                new_io.reset(new_io_file);
                break;
            }
            
            default:
            {
                // Should be unreachable
                fprintf(stderr, "Unexpected redirection type %ld. aborting.\n", (long)redirect_type);
                PARSER_DIE();
                break;
            }
        }
        
        /* Append the new_io if we got one */
        if (new_io.get() != NULL)
        {
            result.push_back(new_io);
        }
    }
    
    if (out_chain && ! errored)
    {
        std::swap(*out_chain, result);
    }
    return ! errored;
}

process_t *parse_execution_context_t::create_boolean_process(job_t *job, const parse_node_t &bool_statement)
{
    // Handle a boolean statement
    bool skip_job = false;
    assert(bool_statement.type == symbol_boolean_statement);
    switch (bool_statement.production_idx)
    {
        // These magic numbers correspond to productions for boolean_statement
        case 0:
            // AND. Skip if the last job failed.
            skip_job = (proc_get_last_status() != 0);
            break;
            
        case 1:
            // OR. Skip if the last job succeeded.
            skip_job = (proc_get_last_status() == 0);
            break;

        case 2:
            // NOT. Negate it.
            job_set_flag(job, JOB_NEGATE, !job_get_flag(job, JOB_NEGATE));
            break;
            
        default:
        {
            fprintf(stderr, "Unexpected production in boolean statement\n");
            PARSER_DIE();
            break;
        }
    }
    
    process_t *result = NULL;
    if (! skip_job)
    {
        const parse_node_t &subject = *tree.get_child(bool_statement, 1, symbol_statement);
        result = this->create_job_process(job, subject);
    }
    return result;
}

process_t *parse_execution_context_t::create_block_process(job_t *job, const parse_node_t &statement_node)
{
    /* We handle block statements by creating INTERNAL_BLOCK_NODE, that will bounce back to us when it's time to execute them */
    assert(statement_node.type == symbol_block_statement || statement_node.type == symbol_if_statement || statement_node.type == symbol_switch_statement);
    
    /* The set of IO redirections that we construct for the process */
    io_chain_t process_io_chain;
    bool errored = ! this->determine_io_chain(statement_node, &process_io_chain);
    if (errored)
        return NULL;

    process_t *result = new process_t();
    result->type = INTERNAL_BLOCK_NODE;
    result->internal_block_node = this->get_offset(statement_node);
    result->set_io_chain(process_io_chain);
    return result;
}


/* Returns a process_t allocated with new. It's the caller's responsibility to delete it (!) */
process_t *parse_execution_context_t::create_job_process(job_t *job, const parse_node_t &statement_node)
{
    assert(statement_node.type == symbol_statement);
    assert(statement_node.child_count == 1);
    
    // Get the "specific statement" which is boolean / block / if / switch / decorated
    const parse_node_t &specific_statement = *get_child(statement_node, 0);
    
    process_t *result = NULL;
    
    switch (specific_statement.type)
    {
        case symbol_boolean_statement:
        {
            result = this->create_boolean_process(job, specific_statement);
            break;
        }
        
        case symbol_block_statement:
        case symbol_if_statement:
        case symbol_switch_statement:
        {
            result = this->create_block_process(job, specific_statement);
            break;
        }
        
        case symbol_decorated_statement:
        {
            /* Get the plain statement. It will pull out the decoration itself */
            const parse_node_t &plain_statement = tree.find_child(specific_statement, symbol_plain_statement);
            result = this->create_plain_process(job, plain_statement);
            break;
        }
        
        default:
            fprintf(stderr, "'%ls' not handled by new parser yet\n", specific_statement.describe().c_str());
            PARSER_DIE();
            break;
    }
    
    return result;
}


bool parse_execution_context_t::populate_job_from_job_node(job_t *j, const parse_node_t &job_node)
{
    assert(job_node.type == symbol_job);
    
    /* Track whether we had an error */
    bool process_errored = false;
    
    /* Tell the job what its command is */
    j->set_command(get_source(job_node));
    
    /* We are going to construct process_t structures for every statement in the job. Get the first statement. */
    const parse_node_t *statement_node = get_child(job_node, 0, symbol_statement);
    assert(statement_node != NULL);
    
    /* Create the process (may fail!) */
    j->first_process = this->create_job_process(j, *statement_node);
    if (j->first_process == NULL)
        process_errored = true;
    
    /* Construct process_ts for job continuations (pipelines), by walking the list until we hit the terminal (empty) job continuation */
    const parse_node_t *job_cont = get_child(job_node, 1, symbol_job_continuation);
    process_t *last_process = j->first_process;
    while (! process_errored && job_cont != NULL && job_cont->child_count > 0)
    {
        assert(job_cont->type == symbol_job_continuation);
        
        /* Handle the pipe */
        const parse_node_t &pipe_node = *get_child(*job_cont, 0, parse_token_type_pipe);
        last_process->pipe_write_fd = fd_redirected_by_pipe(get_source(pipe_node));
        
        /* Get the statement node and make a process from it */
        const parse_node_t *statement_node = get_child(*job_cont, 1, symbol_statement);
        assert(statement_node != NULL);
        
        /* Store the new process (and maybe with an error) */
        last_process->next = this->create_job_process(j, *statement_node);
        if (last_process->next == NULL)
            process_errored = true;

        /* Link the process and get the next continuation */
        last_process = last_process->next;
        job_cont = get_child(*job_cont, 2, symbol_job_continuation);
    }
    
    /* Return success */
    return ! process_errored;
}

int parse_execution_context_t::run_1_job(const parse_node_t &job_node, const block_t *associated_block)
{
    bool log_it = false;
    if (log_it)
    {
        fprintf(stderr, "%s: %ls\n", __FUNCTION__, get_source(job_node).c_str());
    }


    if (should_cancel_execution(associated_block))
    {
        return 1;
    }
    
    // Get terminal modes
    struct termios tmodes = {};
    if (get_is_interactive())
    {
        if (tcgetattr(STDIN_FILENO, &tmodes))
        {
            // need real error handling here
            wperror(L"tcgetattr");
            return EXIT_FAILURE;
        }
    }
    
    /* Increment the eval_level for the duration of this command */
    scoped_push<int> saved_eval_level(&eval_level, eval_level + 1);
    
    /* TODO: blocks-without-redirections optimization */
    
    /* Profiling support */
    long long start_time = 0, parse_time = 0, exec_time = 0;
    const bool do_profile = profile;
    profile_item_t *profile_item = NULL;
    if (do_profile)
    {
        profile_item = new profile_item_t();
        profile_item->skipped = 1;
        profile_items.push_back(profile_item);
        start_time = get_time();
    }
    
    job_t *j = new job_t(acquire_job_id(), block_io);
    job_set_flag(j, JOB_FOREGROUND, 1);
    job_set_flag(j, JOB_TERMINAL, job_get_flag(j, JOB_CONTROL));
    job_set_flag(j, JOB_TERMINAL, job_get_flag(j, JOB_CONTROL) \
                 && (!is_subshell && !is_event));
    job_set_flag(j, JOB_SKIP_NOTIFICATION, is_subshell \
                 || is_block \
                 || is_event \
                 || (!get_is_interactive()));
    job_set_flag(j, JOB_CONTROL,
                 (job_control_mode==JOB_CONTROL_ALL) ||
                 ((job_control_mode == JOB_CONTROL_INTERACTIVE) && (get_is_interactive())));
    
    /* Populate the job. This may fail for reasons like command_not_found */
    bool process_errored = ! this->populate_job_from_job_node(j, job_node);
    
    /* Clean up the job on failure */
    if (process_errored)
    {
        delete j;
        j = NULL;
    }
    
    /* Store time it took to 'parse' the command */
    if (do_profile)
    {
        parse_time = get_time();
        profile_item->cmd = j->command();
        profile_item->skipped=parser->current_block()->skip;
    }
    
    if (! process_errored)
    {
        /* Success. Give the job to the parser - it will clean it up. */
        parser->job_add(j);
        parser->current_block()->job = j;

        /* Check to see if this contained any external commands */
        bool job_contained_external_command = false;
        for (const process_t *proc = j->first_process; proc != NULL; proc = proc->next)
        {
            if (proc->type == EXTERNAL)
            {
                job_contained_external_command = true;
                break;
            }
        }
        
        /* Actually execute the job */
        exec_job(*this->parser, j);
        
        /* Only external commands require a new fishd barrier */
        if (!job_contained_external_command)
        {
            set_proc_had_barrier(false);
        }
    }

    /* Need support for skipped_exec here */
    if (do_profile)
    {
        exec_time = get_time();
        profile_item->level=eval_level;
        profile_item->parse = (int)(parse_time-start_time);
        profile_item->exec=(int)(exec_time-parse_time);
        profile_item->skipped = process_errored;
    }

    /* Set the last status to 1 if the job could not be executed */
    if (process_errored)
        proc_set_last_status(1);
    const int ret = proc_get_last_status();
    
    /* Clean up jobs. Do this after we've determined the return value, since this may trigger event handlers */
    job_reap(0);
    
    /* Output any errors (hack) */
    if (! this->errors.empty())
    {
        fprintf(stderr, "%ls\n", parse_errors_description(this->errors, this->src).c_str());
        this->errors.clear();
    }
    
    /* All done */
    return ret;
}

int parse_execution_context_t::run_job_list(const parse_node_t &job_list_node, const block_t *associated_block)
{
    assert(job_list_node.type == symbol_job_list);
    
    int result = 1;
    const parse_node_t *job_list = &job_list_node;
    while (job_list != NULL && ! should_cancel_execution(associated_block))
    {
        assert(job_list->type == symbol_job_list);
        
        // These correspond to the three productions of job_list
        // Try pulling out a job
        const parse_node_t *job = NULL;
        switch (job_list->production_idx)
        {
            case 0: // empty
                job_list = NULL;
                break;
            
            case 1: //job, job_list
                job = get_child(*job_list, 0, symbol_job);
                job_list = get_child(*job_list, 1, symbol_job_list);
                break;
            
            case 2: //blank line, job_list
                job = NULL;
                job_list = get_child(*job_list, 1, symbol_job_list);
                break;
                
            default: //if we get here, it means more productions have been added to job_list, which is bad
                fprintf(stderr, "Unexpected production in job_list: %lu\n", (unsigned long)job_list->production_idx);
                PARSER_DIE();
        }
        
        if (job != NULL)
        {
            result = this->run_1_job(*job, associated_block);
        }
    }
    
    /* Returns the last job executed */
    return result;
}

int parse_execution_context_t::eval_node_at_offset(node_offset_t offset, const block_t *associated_block, const io_chain_t &io)
{
    bool log_it = false;
    
    /* Don't ever expect to have an empty tree if this is called */
    assert(! tree.empty());
    assert(offset < tree.size());
    
    /* Apply this block IO for the duration of this function */
    scoped_push<io_chain_t> block_io_push(&block_io, io);
    
    const parse_node_t &node = tree.at(offset);
    
    if (log_it)
    {
        fprintf(stderr, "eval node: %ls\n", get_source(node).c_str());
    }
    
    /* Currently, we only expect to execute the top level job list, or a block node. Assert that. */
    assert(node.type == symbol_job_list ||
        node.type == symbol_block_statement ||
        node.type == symbol_if_statement ||
        node.type == symbol_switch_statement);
    
    int status = 1;
    switch (node.type)
    {
        case symbol_job_list:
            /* We should only get a job list if it's the very first node. This is because this is the entry point for both top-level execution (the first node) and INTERNAL_BLOCK_NODE execution (which does block statements, but never job lists) */
            assert(offset == 0);
            status = this->run_job_list(node, associated_block);
            break;
        
        case symbol_block_statement:
            status = this->run_block_statement(node);
            break;
            
        case symbol_if_statement:
            status = this->run_if_statement(node);
            break;
            
        case symbol_switch_statement:
            status = this->run_switch_statement(node);
            break;
            
        default:
            /* In principle, we could support other node types. However we never expect to be passed them - see above. */
            fprintf(stderr, "Unexpected node %ls found in %s\n", node.describe().c_str(), __FUNCTION__);
            PARSER_DIE();
            break;
    }
    
    proc_set_last_status(status);
    
    /* Argh */
    int ret = errors.empty() ? 0 : 1;
    errors.clear();
    return ret;
}