[interactive] Respect OILS_COMP_UI in oshrc/yshrc (#2244)

You can do

    # oshrc
    OILS_COMP_UI=nice

Rather than

    osh  --completion-display nice

- Update docs
- add test/manual.sh - thinking about ENV.OILS_COMP_UI issue

---------

Co-authored-by: Andy C <[email protected]>

Author: melvinw

core/shell.py

@@ -1082,8 +1082,21 @@ def Main(
         mutable_opts.set_redefine_const()
         mutable_opts.set_redefine_source()
 
+        # NOTE: rc files loaded AFTER _InitDefaultCompletions.
+        for rc_path in rc_paths:
+            with state.ctx_ThisDir(mem, rc_path):
+                try:
+                    SourceStartupFile(fd_state, rc_path, lang, parse_ctx,
+                                      cmd_ev, errfmt)
+                except util.UserExit as e:
+                    return e.status
+
+        completion_display = state.MaybeString(mem, 'OILS_COMP_UI')
+        if completion_display is None:
+            completion_display = flag.completion_display
+
         if readline:
-            if flag.completion_display == 'nice':
+            if completion_display == 'nice':
                 display = comp_ui.NiceDisplay(comp_ui_state, prompt_state,
                     debug_f, readline, signal_safe)  # type: comp_ui._IDisplay
             else:
@@ -1101,21 +1114,11 @@ def Main(
                                              debug_f, signal_safe)
 
         process.InitInteractiveShell(signal_safe)  # Set signal handlers
-
         # The interactive shell leads a process group which controls the terminal.
         # It MUST give up the terminal afterward, otherwise we get SIGTTIN /
         # SIGTTOU bugs.
         with process.ctx_TerminalControl(job_control, errfmt):
 
-            # NOTE: rc files loaded AFTER _InitDefaultCompletions.
-            for rc_path in rc_paths:
-                with state.ctx_ThisDir(mem, rc_path):
-                    try:
-                        SourceStartupFile(fd_state, rc_path, lang, parse_ctx,
-                                          cmd_ev, errfmt)
-                    except util.UserExit as e:
-                        return e.status
-
             assert line_reader is not None
             line_reader.Reset()  # After sourcing startup file, render $PS1
 

doc/ref/chap-special-var.md

@@ -379,6 +379,17 @@ Override the default OSH history location.
 
 Override the default YSH history location.
 
+## Interactive
+
+### OILS_COMP_UI
+
+Set which completion UI to use. Defaults to `minimal`.
+
+- `minimal` - a UI that approximates the default behavior of GNU readline.
+- `nice` - a UI with a fancy pager and a prompt with horizontal scrolling instead of wrapping.
+
+This variable is currently only checked once during shell initialization.
+
 ## cd
 
 ### PWD

doc/ref/toc-osh.md

@@ -199,6 +199,7 @@ X [Unsupported]   enable
 </h2>
 
 ```chapter-links-special-var
+  [Interactive]   OILS_COMP_UI
   [Oils VM]       OILS_VERSION      LIB_OSH
   [POSIX Special] $@  $*  $#     $?  $-     $$  $!   $0  $9
   [Shell Vars]    IFS             X LANG       X GLOBIGNORE

doc/ref/toc-ysh.md

@@ -366,6 +366,7 @@ X [External Lang] BEGIN   END   when (awk)
   [YSH Tracing]   SHX_indent          SHX_punct             SHX_pid_str
   [YSH read]      _reply
   [History]       YSH_HISTFILE
+  [Interactive]   OILS_COMP_UI
   [Oils VM]       OILS_VERSION
                   OILS_GC_THRESHOLD   OILS_GC_ON_EXIT
                   OILS_GC_STATS       OILS_GC_STATS_FD

test/manual.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+#
+# Manual tests
+#
+# Usage:
+#   test/manual.sh <function name>
+
+: ${LIB_OSH=stdlib/osh}
+source $LIB_OSH/bash-strict.sh
+source $LIB_OSH/task-five.sh
+
+readonly OSHRC=_tmp/manual-oshrc
+
+setup() {
+  cat >$OSHRC <<EOF
+OILS_COMP_UI=nice
+EOF
+}
+
+test-osh() {
+  # Test it manually
+  bin/osh --rcfile $OSHRC
+}
+
+test-ysh() {
+  # same OSHRC?  Should it respect ENV.OILS_COMP_UI?
+  bin/ysh --rcfile $OSHRC
+}
+
+task-five "$@"