More improvements

Author: jorenby

docs/source/configuration/layout.rst

@@ -192,15 +192,27 @@ up visually in the editor, regardless of the rendered length of
 Advanced: coordinate space override
 -----------------------------------
 
-You can optionally force the coordinate space via the alignment constraint by
-adding a final modifier to the align value (available for spacing_before and
-spacing_after):
+You can optionally force the coordinate space either:
+
+1) via the alignment constraint suffix (available for `spacing_before` and
+   `spacing_after`), or
+2) via the `alignment_coordinate_space` key in layout config for the target type.
 
 .. code-block:: ini
 
    [sqlfluff:layout:type:alias_expression]
    spacing_before = align:alias_expression:select_clause:bracketed:source
 
+Alternatively, the equivalent can be configured more declaratively:
+
+.. code-block:: ini
+
+   [sqlfluff:layout:type:alias_expression]
+   spacing_before = align
+   align_within = select_clause
+   align_scope = bracketed
+   alignment_coordinate_space = source
+
 Supported values are ``source`` and ``templated``. In most cases, ``source`` is
 the recommended choice for readability.
 

src/sqlfluff/utils/reflow/respace.py

@@ -404,9 +404,12 @@ def _determine_aligned_inline_spacing(
         if seg.is_code:
             last_code = seg
 
-    # Compute desired whitespace size in the chosen coordinate space
+    # Compute desired whitespace size in the chosen coordinate space.
+    # Ensure we always return at least a single space to avoid deleting
+    # whitespace when the current position already exceeds the target.
     current_ws_pos = _pos_col(whitespace_seg.pos_marker, use_source_positions)
-    desired_space = " " * (1 + max_desired_line_pos - current_ws_pos)
+    pad_width = max(1, 1 + max_desired_line_pos - current_ws_pos)
+    desired_space = " " * pad_width
     reflow_logger.debug(
         "    desired_space: %r (based on max line pos of %s)",
         desired_space,

test/rules/std_LT01_jinja_alignment_test.py

@@ -64,3 +64,37 @@ def test_lt01_alias_alignment_with_jinja_uses_source_positions() -> None:
     first_as_col = select_lines[0].index(" as ")
     second_as_col = select_lines[1].index(" as ")
     assert first_as_col == second_as_col
+
+
+def test_lt01_alias_alignment_with_jinja_coordinate_space_config_key() -> None:
+    """Coordinate space can be set via alignment_coordinate_space config key."""
+    sql = "select\n" "    {{ 'templ' }} as a,\n" "    b as bb\n"
+
+    cfg = FluffConfig.from_kwargs(dialect="ansi")
+    cfg._configs["core"]["templater"] = "jinja"
+    cfg._configs.setdefault("templater", {}).setdefault("jinja", {}).setdefault(
+        "context", {}
+    )
+    # Force templated coordinate space via config key enrichment path
+    cfg._configs.setdefault("layout", {}).setdefault("type", {}).setdefault(
+        "alias_expression", {}
+    ).update(
+        {
+            "spacing_before": "align",
+            "align_within": "select_clause",
+            "align_scope": "bracketed",
+            "alignment_coordinate_space": "templated",
+        }
+    )
+
+    fixed = sqlfluff.fix(sql, config=cfg, rules=["LT01"])
+    # With templated coordinate space, the second line pads less
+    lines = fixed.splitlines()
+    assert any(" as " in line for line in lines)
+    select_lines = [line for line in lines if " as " in line]
+    assert len(select_lines) == 2
+    # Check that there is at least some padding before 'as' on second line
+    # but not necessarily aligned to the source position of the templated value.
+    first_as_col = select_lines[0].index(" as ")
+    second_as_col = select_lines[1].index(" as ")
+    assert second_as_col <= first_as_col