Teach builtin_string to recognize redirections, not just pipes

Allows cases like `string split \n < file.txt` to work.
Fixes 2422

4 files changed, 21 insertions, 6 deletions

diff --git a/src/builtin_string.cpp b/src/builtin_string.cpp
index 22f16fc6..a35903cb 100644
--- a/src/builtin_string.cpp
+++ b/src/builtin_string.cpp
@@ -54,7 +54,7 @@ static void string_unknown_option(parser_t &parser, io_streams_t &streams, const
 /* We read from stdin if we are the second or later process in a pipeline. */
 static bool string_args_from_stdin(const io_streams_t &streams)
 {
-    return ! streams.is_first_process_in_pipeline;
+    return streams.stdin_is_directly_redirected;
 }
 
 static const wchar_t *string_get_arg_stdin(wcstring *storage, const io_streams_t &streams)
diff --git a/src/exec.cpp b/src/exec.cpp
index 5366e663..e4ae5104 100644
--- a/src/exec.cpp
+++ b/src/exec.cpp
@@ -953,11 +953,25 @@ void exec_job(parser_t &parser, job_t *j)
                 }
                 else
                 {
+                    // Determine if we have a "direct" redirection for stdin
+                    bool stdin_is_directly_redirected;
+                    if (p != j->first_process)
+                    {
+                        // We must have a pipe
+                        stdin_is_directly_redirected = true;
+                    }
+                    else
+                    {
+                        // We are not a pipe. Check if there is a redirection local to the process that's not IO_CLOSE
+                        const shared_ptr<const io_data_t> stdin_io = io_chain_get(p->io_chain(), STDIN_FILENO);
+                        stdin_is_directly_redirected = stdin_io && stdin_io->io_mode != IO_CLOSE;
+                    }
+                    
                     builtin_io_streams.reset(new io_streams_t());
                     builtin_io_streams->stdin_fd = local_builtin_stdin;
                     builtin_io_streams->out_is_redirected = has_fd(process_net_io_chain, STDOUT_FILENO);
                     builtin_io_streams->err_is_redirected = has_fd(process_net_io_chain, STDERR_FILENO);
-                    builtin_io_streams->is_first_process_in_pipeline = (p == j->first_process);
+                    builtin_io_streams->stdin_is_directly_redirected = stdin_is_directly_redirected;
                     builtin_io_streams->io_chain = &process_net_io_chain;
 
                     
diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index 1b71411c..889dfbb8 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -4024,7 +4024,7 @@ static void run_one_string_test(const wchar_t **argv, int expected_rc, const wch
 {
     parser_t parser(PARSER_TYPE_GENERAL, true);
     io_streams_t streams;
-    streams.is_first_process_in_pipeline = true; // read from argv instead of stdin
+    streams.stdin_is_directly_redirected = false; // read from argv instead of stdin
     int rc = builtin_string(parser, streams, const_cast<wchar_t**>(argv));
     wcstring args;
     for (int i = 0; argv[i] != 0; i++)
diff --git a/src/io.h b/src/io.h
index 8d12f685..bb4c0621 100644
--- a/src/io.h
+++ b/src/io.h
@@ -288,8 +288,9 @@ struct io_streams_t
     // fd representing stdin. This is not closed by the destructor.
     int stdin_fd;
     
-    // Whether this is the first process in a pipeline
-    bool is_first_process_in_pipeline;
+    // Whether stdin is "directly redirected," meaning it is the recipient of a pipe (foo | cmd) or direct redirection (cmd < foo.txt)
+    // An "indirect redirection" would be e.g. begin ; cmd ; end < foo.txt
+    bool stdin_is_directly_redirected;
     
     // Indicates whether stdout and stderr are redirected (e.g. to a file or piped)
     bool out_is_redirected;
@@ -298,7 +299,7 @@ struct io_streams_t
     // Actual IO redirections. This is only used by the source builtin. Unowned.
     const io_chain_t *io_chain;
     
-    io_streams_t() : stdin_fd(-1), is_first_process_in_pipeline(false), out_is_redirected(false), err_is_redirected(false), io_chain(NULL)
+    io_streams_t() : stdin_fd(-1), stdin_is_directly_redirected(false), out_is_redirected(false), err_is_redirected(false), io_chain(NULL)
     {
     }
 };