enable old style single-line annotations with --annotation-style=line

piptools/scripts/compile.py

@@ -123,6 +123,12 @@ def _get_default_option(option_name: str) -> Any:
     default=True,
     help="Annotate results, indicating where dependencies come from",
 )
+@click.option(
+    "--annotation-style",
+    type=click.Choice(("line", "split")),
+    default="split",
+    help="Choose the format of annotation comments",
+)
 @click.option(
     "-U",
     "--upgrade/--no-upgrade",
@@ -244,6 +250,7 @@ def cli(
     header: bool,
     emit_trusted_host: bool,
     annotate: bool,
+    annotation_style: str,
     upgrade: bool,
     upgrade_packages: Tuple[str, ...],
     output_file: Union[LazyFile, IO[Any], None],
@@ -471,6 +478,7 @@ def cli(
         emit_index_url=emit_index_url,
         emit_trusted_host=emit_trusted_host,
         annotate=annotate,
+        annotation_style=annotation_style,
         strip_extras=strip_extras,
         generate_hashes=generate_hashes,
         default_index_url=repository.DEFAULT_INDEX_URL,

piptools/writer.py

@@ -51,6 +51,23 @@ def _comes_from_as_string(ireq: InstallRequirement) -> str:
     return key_from_ireq(ireq.comes_from)
 
 
+def annotation_style_split(required_by: Set[str]) -> str:
+    sorted_required_by = sorted(required_by)
+    if len(sorted_required_by) == 1:
+        source = sorted_required_by[0]
+        annotation = "# via " + source
+    else:
+        annotation_lines = ["# via"]
+        for source in sorted_required_by:
+            annotation_lines.append("    #   " + source)
+        annotation = "\n".join(annotation_lines)
+    return annotation
+
+
+def annotation_style_line(required_by: Set[str]) -> str:
+    return f"# via {', '.join(sorted(required_by))}"
+
+
 class OutputWriter:
     def __init__(
         self,
@@ -61,6 +78,7 @@ def __init__(
         emit_index_url: bool,
         emit_trusted_host: bool,
         annotate: bool,
+        annotation_style: str,
         strip_extras: bool,
         generate_hashes: bool,
         default_index_url: str,
@@ -79,6 +97,7 @@ def __init__(
         self.emit_index_url = emit_index_url
         self.emit_trusted_host = emit_trusted_host
         self.annotate = annotate
+        self.annotation_style = annotation_style
         self.strip_extras = strip_extras
         self.generate_hashes = generate_hashes
         self.default_index_url = default_index_url
@@ -258,15 +277,14 @@ def _format_requirement(
             required_by.add(_comes_from_as_string(ireq))
 
         if required_by:
-            sorted_required_by = sorted(required_by)
-            if len(sorted_required_by) == 1:
-                source = sorted_required_by[0]
-                annotation = "    # via " + source
-            else:
-                annotation_lines = ["    # via"]
-                for source in sorted_required_by:
-                    annotation_lines.append("    #   " + source)
-                annotation = "\n".join(annotation_lines)
-            line = f"{line}\n{comment(annotation)}"
+            annotation = {
+                "split": annotation_style_split,
+                "line": annotation_style_line,
+            }[self.annotation_style](required_by)
+            sep = {"split": "\n    ", "line": "\n    " if ireq_hashes else "  "}[
+                self.annotation_style
+            ]
+            lines = f"{line:24}{sep}{comment(annotation)}".splitlines()
+            line = "\n".join(ln.rstrip() for ln in lines)
 
         return line

tests/test_writer.py

@@ -36,6 +36,7 @@ def writer(tmpdir_cwd):
             emit_index_url=True,
             emit_trusted_host=True,
             annotate=True,
+            annotation_style="split",
             generate_hashes=False,
             default_index_url=None,
             index_urls=[],
@@ -57,37 +58,37 @@ def test_format_requirement_annotation_editable(from_editable, writer):
 
     assert writer._format_requirement(
         ireq
-    ) == "-e git+git://fake.org/x/y.git#egg=y\n" + comment("    # via xyz")
+    ) == "-e git+git://fake.org/x/y.git#egg=y\n    " + comment("# via xyz")
 
 
 def test_format_requirement_annotation(from_line, writer):
     ireq = from_line("test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
 
 
 def test_format_requirement_annotation_lower_case(from_line, writer):
     ireq = from_line("Test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
 
 
 def test_format_requirement_for_primary(from_line, writer):
     "Primary packages should get annotated."
     ireq = from_line("test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
 
 
 def test_format_requirement_for_primary_lower_case(from_line, writer):
     "Primary packages should get annotated."
     ireq = from_line("Test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
 
 
 def test_format_requirement_environment_marker(from_line, writer):