Draft `SOFT_NL`: add new line character if the prompt end is near terminal border.

docs/tutorial.rst

@@ -1656,6 +1656,7 @@ By default, the following variables are available for use:
   * ``time_format``: A time format string, defaulting to ``"%H:%M:%S"``.
   * ``last_return_code``: The return code of the last issued command.
   * ``last_return_code_if_nonzero``: The return code of the last issued command if it is non-zero, otherwise ``None``. This is useful for only printing the code in case of errors.
+  * ``SOFT_NL``: add new line character if the prompt end is near terminal border.
 
 .. note:: See the section below on ``PROMPT_FIELDS`` for more information on changing.
 

xonsh/prompt/base.py

@@ -144,14 +144,14 @@ def default_prompt():
         dp = (
             "{YELLOW}{env_name}{RESET}"
             "{BOLD_GREEN}{user}@{hostname}"
-            "{BOLD_BLUE} {cwd} {prompt_end}{RESET} "
+            "{BOLD_BLUE} {cwd} {SOFT_NL}{prompt_end}{RESET} "
         )
     elif xp.ON_WINDOWS and not xp.win_ansi_support():
         dp = (
             "{YELLOW}{env_name}{RESET}"
             "{BOLD_INTENSE_GREEN}{user}@{hostname}{BOLD_INTENSE_CYAN} "
             "{cwd}{branch_color}{curr_branch: {}}{RESET} "
-            "{BOLD_INTENSE_CYAN}{prompt_end}{RESET} "
+            "{SOFT_NL}{BOLD_INTENSE_CYAN}{prompt_end}{RESET} "
         )
     else:
         dp = (
@@ -159,7 +159,7 @@ def default_prompt():
             "{BOLD_GREEN}{user}@{hostname}{BOLD_BLUE} "
             "{cwd}{branch_color}{curr_branch: {}}{RESET} "
             "{RED}{last_return_code_if_nonzero:[{BOLD_INTENSE_RED}{}{RED}] }{RESET}"
-            "{BOLD_BLUE}{prompt_end}{RESET} "
+            "{SOFT_NL}{BOLD_BLUE}{prompt_end}{RESET} "
         )
     return dp
 

xonsh/ptk_shell/shell.py

@@ -440,6 +440,27 @@ class PromptToolkitShell(BaseShell):
                 else:
                     break
 
+    def _replace_soft_nl(self, toks):
+        """Replace ``{SOFT_NL}`` tag to new line."""
+        SOFT_NL = '{SOFT_NL}'
+        prompt_len = 0
+        soft_nl_pos = None
+        for i, t in enumerate(toks):
+            nt = t[1].replace(SOFT_NL, '')
+            prompt_len += len(nt)
+            if len(t[1]) != len(nt):
+                soft_nl_pos = i
+
+        if soft_nl_pos is not None:
+            try:
+                import shutil
+                term_w, h = shutil.get_terminal_size()
+                c = '\n' if (term_w - prompt_len%term_w) < 10 else ''
+                toks[soft_nl_pos] = (toks[soft_nl_pos][0], toks[soft_nl_pos][1].replace(SOFT_NL, c))
+            except:
+                toks[soft_nl_pos] = (toks[soft_nl_pos][0], toks[soft_nl_pos][1].replace(SOFT_NL, ''))
+        return toks
+
     def _get_prompt_tokens(self, env_name: str, prompt_name: str, **kwargs):
         env = XSH.env  # type:ignore
         p = env.get(env_name)
@@ -455,7 +476,7 @@ class PromptToolkitShell(BaseShell):
             print_exception()
 
         toks = partial_color_tokenize(p)
-
+        toks = self._replace_soft_nl(toks)
         return tokenize_ansi(PygmentsTokens(toks))
 
     def prompt_tokens(self):