Set TERM to dumb by default

byexample/init.py

@@ -443,6 +443,12 @@ def get_default_options_parser(cmdline_args):
         help=
         "select a terminal emulator to interpret the output (default to 'dumb')."
     )
+    options_parser.add_argument(
+        "+term-type",
+        default='dumb',
+        help=
+        "set the TERM env var for the interpreters/runners (default to 'dumb', other values could be 'vt100'); if left empty, leave it unset."
+    )
 
     options_parser.add_flag(
         "type",

byexample/runner.py

@@ -348,8 +348,15 @@ def _spawn_interpreter(
         env = os.environ.copy()
         if env_update:
             env.update(env_update)
+
+        # Override the environment with LINES, COLUMNS (from geometry)
         env.update({'LINES': str(rows), 'COLUMNS': str(cols)})
 
+        # With TERM=dumb is the safest option, TERM=vt100 may be needed to offer a dummy
+        # *but* functional TERM because some programs may print scary "WARNING: terminal is not fully functional"
+        term_kind = options['term_type'].strip()
+        env.update({'TERM': term_kind})
+
         self._drop_output()  # there shouldn't be any output yet but...
         self._cmd = cmd
 
@@ -573,16 +580,26 @@ def _exec_and_wait(self, source, options, *, from_example=None, **kargs):
         countdown = Countdown(timeout)
         lines = source.split('\n')
 
+        if clog().isEnabledFor(DEBUG):
+            with log_with("sendlines") as clog2:
+                clog2.debug("\n > " + '\n > '.join(lines))
+
         self._last_num_lines_sent = 0
         for line in lines[:-1]:
             with profile_ctx("sendline"):
+                # turn the echo off (may be)
+                self._may_turn_echo_off(options)
+
                 self._sendline(line)
                 self._last_num_lines_sent += 1
             self._expect_prompt_or_type(
                 options, countdown, input_list=input_list
             )
 
         with profile_ctx("sendline"):
+            # turn the echo off (may be)
+            self._may_turn_echo_off(options)
+
             self._sendline(lines[-1])
             self._last_num_lines_sent += 1
 

docs/advanced/terminal-emulation.md

@@ -17,7 +17,6 @@ is fast and works well in most cases.
 
 But you can change this to disable emulation with ``+term=as-is`` or
 to enable full ANSI terminal emulation with ``+term=ansi``.
-
 ## Dumb terminal
 
 In this mode, ``byexample`` emulates a very simple terminal, processing
@@ -104,9 +103,9 @@ It can be useful in some special cases to check white spaces
 that are removed by the dumb or ANSI terminals.
 
 ```python
->>> print("\tfoo\tbar\nbaz\tsaz    \rtaz")       # byexample: +term=as-is
+>>> print("\tfoo\tbar\nbaz\tsaz\rtaz")       # byexample: +term=as-is
 	foo	bar
-baz	saz    
+baz	saz
 taz
 ```
 
@@ -163,7 +162,7 @@ that use ``ncurses``) and require a terminal emulator.
 Examples of this are programs like ``less``, ``more``, ``top`` and ``man``.
 
 ```shell
-$ less test/ds/python-tutorial.v2.md # byexample: +term=ansi +rm=  +stop-on-timeout
+$ TERM=vt100 less test/ds/python-tutorial.v2.md # byexample: +term=ansi +rm=  +stop-on-timeout
  This is a 101 Python tutorial
  The following is an example written in Python about arithmetics
 
@@ -212,6 +211,50 @@ line 32
 If this is a problem change the [geometry](/{{ site.uprefix }}/advanced/geometry):
 increase the count of rows that the terminal has with ``+geometry``.
 
+## ``TERM`` environment variable
+
+While the ``+term`` controls how the *output* is emulated and can be
+changed per example, ``byexample`` also sets the ``TERM`` environment
+variable to indicate the interpreter (and possible any subprogram
+executed by it) that the terminal if of a particular type.
+
+Contrary to ``+term``, ``+term-type`` has effect only if it is set
+in the command line before the interpreters are started and it cannot be
+changed later.
+
+By default, ``byexample`` sets ``TERM=dumb`` to indicate a
+zero-capabilites terminal. You can change this setting from
+the command line with ``-o +term-type=vt100`` (``vt100`` indicates a
+basic but functional terminal).
+
+```shell
+$ byexample -l shell test/ds/echo-term-env-variable.md
+<...>
+TERM=dumb
+<...>
+
+$ byexample -l shell -o +term-type=vt100 test/ds/echo-term-env-variable.md
+<...>
+TERM=vt100
+<...>
+```
+
+If you want to use the same ``TERM`` value that your real terminal has,
+you can pass it (nothing special is needed):
+
+```shell
+$ TERM=xterm
+$ byexample -l shell -o +term-type=$TERM test/ds/echo-term-env-variable.md
+<...>
+TERM=xterm
+<...>
+```
+
+> *Changed* in `byexample 11.0.0`. Before `11.0.0.` the `TERM` variable
+> was inherit from the caller's environment. Starting from `11.0.0`
+> this is not longer the case. If you need the old behavior,
+> do `-o +term-type=$TERM` as shown above.
+
 <!--
 
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