fix: remove trailing spaces where supported (#210)

Fixes #136

craft_cli/printer.py

@@ -19,6 +19,8 @@
 
 import itertools
 import math
+import os
+import platform
 import queue
 import shutil
 import threading
@@ -44,6 +46,8 @@
 # craft_cli/pytest_plugin.py )
 TESTMODE = False
 
+ANSI_CLEAR_LINE_TO_END = "\033[K"  # ANSI escape code to clear the rest of the line.
+
 
 @dataclass
 class _MessageInfo:
@@ -71,7 +75,25 @@ def _get_terminal_width() -> int:
     return shutil.get_terminal_size().columns
 
 
-def _format_term_line(prefix: str, text: str, spintext: str, *, ephemeral: bool) -> str:
+@lru_cache
+def _supports_ansi_escape_sequences() -> bool:
+    """Whether the current environment supports ANSI escape sequences."""
+    if platform.system() != "Windows":
+        return True
+    return "WT_SESSION" in os.environ  # Windows Terminal supports ANSI escape sequences.
+
+
+def _fill_line(text: str) -> str:
+    """Turn the input text into a line that will fill the terminal."""
+    if _supports_ansi_escape_sequences():
+        return text + ANSI_CLEAR_LINE_TO_END
+    width = _get_terminal_width()
+    # Fill the line but leave one character for the cursor.
+    n_spaces = width - len(text) % width - 1
+    return text + " " * n_spaces
+
+
+def _format_term_line(previous_line_end: str, text: str, spintext: str, *, ephemeral: bool) -> str:
     """Format a line to print to the terminal."""
     # fill with spaces until the very end, on one hand to clear a possible previous message,
     # but also to always have the cursor at the very end
@@ -87,9 +109,8 @@ def _format_term_line(prefix: str, text: str, spintext: str, *, ephemeral: bool)
             text = text[-remaining_for_last_line:]
             if len(text) > usable:
                 text = text[: usable - 1] + "…"
-    cleaner = " " * (usable - len(text) % width)
 
-    return prefix + text + spintext + cleaner
+    return previous_line_end + _fill_line(text + spintext)
 
 
 class _Spinner(threading.Thread):
@@ -226,38 +247,60 @@ def _get_prefixed_message_text(self, message: _MessageInfo) -> str:
 
         return text
 
+    def _get_line_end(self, spintext: str) -> str:
+        """Get the end of line to use when writing a line to the terminal."""
+        if spintext:
+            # forced to overwrite the previous message to present the spinner
+            return "\r"
+        if self.prv_msg is None or self.prv_msg.end_line:
+            # first message, or previous message completed the line: start clean
+            return ""
+        if self.prv_msg.ephemeral:
+            # the last one was ephemeral, overwrite it
+            return "\r"
+        # Previous line was ended; complete it.
+        return "\n"
+
     def _write_line_terminal(self, message: _MessageInfo, *, spintext: str = "") -> None:
         """Write a simple line message to the screen."""
-        # prepare the text with (maybe) the timestamp
-        text = self._get_prefixed_message_text(message)
+        # prepare the text with (maybe) the timestamp and remove trailing spaces
+        text = self._get_prefixed_message_text(message).rstrip()
 
         if message.use_timestamp:
             timestamp_str = message.created_at.isoformat(sep=" ", timespec="milliseconds")
             text = f"{timestamp_str} {text}"
 
-        if spintext:
-            # forced to overwrite the previous message to present the spinner
-            maybe_cr = "\r"
-        elif self.prv_msg is None or self.prv_msg.end_line:
-            # first message, or previous message completed the line: start clean
-            maybe_cr = ""
-        elif self.prv_msg.ephemeral:
-            # the last one was ephemeral, overwrite it
-            maybe_cr = "\r"
-            if self.prv_msg.stream != message.stream:
-                # If the last message's stream is different from this new one,
-                # send the carriage return to the original stream only.
-                print(maybe_cr, flush=True, file=self.prv_msg.stream, end="")
-                maybe_cr = ""
-        else:
-            # complete the previous line, leaving that message ok
-            maybe_cr = ""
+        previous_line_end = self._get_line_end(spintext)
+        if self.prv_msg and self.prv_msg.ephemeral and self.prv_msg.stream != message.stream:
+            # If the last message's stream is different from this new one,
+            # send a carriage return to the original stream only.
+            print("\r", flush=True, file=self.prv_msg.stream, end="")
+            previous_line_end = ""
+        if self.prv_msg and previous_line_end == "\n":
+            previous_line_end = ""
             print(flush=True, file=self.prv_msg.stream)
 
+        # fill with spaces until the very end, on one hand to clear a possible previous message,
+        # but also to always have the cursor at the very end
+        width = _get_terminal_width()
+        usable = width - len(spintext) - 1  # the 1 is the cursor itself
+        if len(text) > usable:
+            if message.ephemeral:
+                text = text[: usable - 1] + "…"
+            elif spintext:
+                # we need to rewrite the message with the spintext, use only the last line for
+                # multiline messages, and ensure (again) that the last real line fits
+                remaining_for_last_line = len(text) % width
+                text = text[-remaining_for_last_line:]
+                if len(text) > usable:
+                    text = text[: usable - 1] + "…"
+
         # We don't need to rewrite the same ephemeral message repeatedly.
         should_overwrite = spintext or message.end_line or not message.ephemeral
         if should_overwrite or message != self.prv_msg:
-            line = _format_term_line(maybe_cr, text, spintext, ephemeral=message.ephemeral)
+            line = _format_term_line(
+                previous_line_end, text, spintext, ephemeral=message.ephemeral
+            )
             print(line, end="", flush=True, file=message.stream)
 
         if message.end_line:

tests/integration/test_messages_integration.py

@@ -86,21 +86,24 @@ class Line:
     regex: bool = False  # if "text" is a regular expression instead of an exact string
 
 
-def compare_lines(expected_lines: Collection[Line], raw_stream, std_stream):
+def compare_lines(expected_lines: Collection[Line], raw_stream: str, std_stream):
     """Helper to compare expected lines to what was written to the terminal."""
     width = printer._get_terminal_width()
     terminal = printer._stream_is_terminal(std_stream)
     if expected_lines:
         assert len(raw_stream) > 0
 
     if terminal:
-        # when showing to the terminal, it's completed always to screen width and terminated in
-        # different ways, so we split lines according to that length
-        assert (
-            len(raw_stream) % width == 0
-        ), f"Bad length {len(raw_stream)} ({width=}) {raw_stream=!r}"
-        args = [iter(raw_stream)] * width
-        lines = ["".join(x) for x in zip(*args)]  # pyright: ignore[reportGeneralTypeIssues]
+        if printer._supports_ansi_escape_sequences():
+            lines = raw_stream.replace("\033[K", "").splitlines(keepends=True)
+        else:
+            # If the terminal doesn't support ANSI escape sequences, we fill the screen
+            # width and don't terminate lines, so we split lines according to that length
+            assert (
+                len(raw_stream) % width == 0
+            ), f"Bad length {len(raw_stream)} ({width=}) {raw_stream=!r}"
+            args = [iter(raw_stream)] * width
+            lines = ["".join(x) for x in zip(*args)]  # pyright: ignore[reportGeneralTypeIssues]
     else:
         # when the output is captured, each line is simple and it should end in newline, so use
         # that for splitting (but don't lose the newline)
@@ -1528,7 +1531,7 @@ def test_streaming_brief_spinner(capsys, logger, monkeypatch, init_emitter):
         Line("Begin stage", permanent=False),
         Line("Begin stage :: Opening stream", permanent=False),
         Line("Begin stage :: Info message", permanent=False),
-        Line(r"Begin stage :: Info message - \(0.[7-9]s\)", permanent=False, regex=True),
+        Line(r"Begin stage :: Info message - \((0.[7-9]|1.0)s\)", permanent=False, regex=True),
         Line("Begin stage :: Info message", permanent=False),
         Line("Done stage", permanent=True),
     ]