Fix symbol library resolution on macOS and without a sym-lib-table

Two bugs left built-in symbols (Device, Connector, ...) unresolvable, which
cascaded into every batch place/label/wire producing zero results:

- get_kicad_symbol_dir() only checked KICAD9/KICAD8_SYMBOL_DIR and a single
  Linux path. It ignored the generic KICAD_SYMBOL_DIR, KiCad 10, and the
  macOS/Windows install locations, so it returned None on macOS even with the
  symbols present. Now checks KICAD_SYMBOL_DIR + KICAD{10,9,8,7}_SYMBOL_DIR and
  per-platform default paths.
- resolve_library_path() never searched the system symbol directory for
  <lib>.kicad_sym; the system dir was only used for variable substitution
  inside a sym-lib-table. With no table configured (tests, fresh installs),
  built-in libraries were unreachable. Added a system-dir fallback and covered
  the KiCad 10/7 global-table config dirs.

Update test_env_override to clear ambient symbol-dir vars so the override under
test is decisive regardless of the host environment.

src/mckicad/utils/lib_resolver.py

@@ -106,9 +106,12 @@ def resolve_library_path(
 
     Search order:
     1. Project sym-lib-table (if project_dir given)
-    2. Global sym-lib-table (KiCad 9, then 8)
+    2. Global sym-lib-table (KiCad 10, 9, 8, 7)
     3. Direct file search (project dir, libs/, ../libs/)
+    4. System symbol directory (built-in libraries like Device)
     """
+    filename = f"{library_name}.kicad_sym"
+
     # 1. Project sym-lib-table
     if project_dir:
         table_path = os.path.join(project_dir, "sym-lib-table")
@@ -119,8 +122,8 @@ def resolve_library_path(
                 if os.path.isfile(uri):
                     return uri
 
-    # 2. Global sym-lib-tables (KiCad 9 first, then 8)
+    # 2. Global sym-lib-tables (newest KiCad first)
-    for version_dir in ("9.0", "8.0"):
+    for version_dir in ("10.0", "9.0", "8.0", "7.0"):
         config_dir = os.path.expanduser(f"~/.config/kicad/{version_dir}")
         table_path = os.path.join(config_dir, "sym-lib-table")
         if os.path.isfile(table_path):
@@ -132,7 +135,6 @@ def resolve_library_path(
 
     # 3. Direct file search (fallback for projects without sym-lib-table)
     if project_dir:
-        filename = f"{library_name}.kicad_sym"
         candidates = [
             os.path.join(project_dir, filename),
             os.path.join(project_dir, "libs", filename),
@@ -143,6 +145,14 @@ def resolve_library_path(
             if os.path.isfile(resolved):
                 return resolved
 
+    # 4. System symbol directory (built-in libraries, e.g. Device, Connector).
+    # This is the authoritative source when no sym-lib-table is configured.
+    symbol_dir = get_kicad_symbol_dir()
+    if symbol_dir:
+        resolved = os.path.join(symbol_dir, filename)
+        if os.path.isfile(resolved):
+            return resolved
+
     return None
 
 
@@ -249,16 +259,33 @@ def extract_symbol_sexp_text(
 def get_kicad_symbol_dir() -> str | None:
     """Detect the KiCad system symbol directory.
 
-    Checks ``KICAD9_SYMBOL_DIR`` and ``KICAD8_SYMBOL_DIR`` env vars,
+    Checks, in order, the generic ``KICAD_SYMBOL_DIR`` env var, the
-    then falls back to the standard Linux install path.
+    version-specific ``KICAD{10,9,8,7}_SYMBOL_DIR`` vars, then the standard
+    install paths for macOS, Linux, and Windows.
     """
-    for env_var in ("KICAD9_SYMBOL_DIR", "KICAD8_SYMBOL_DIR"):
+    for env_var in (
+        "KICAD_SYMBOL_DIR",
+        "KICAD10_SYMBOL_DIR",
+        "KICAD9_SYMBOL_DIR",
+        "KICAD8_SYMBOL_DIR",
+        "KICAD7_SYMBOL_DIR",
+    ):
         val = os.environ.get(env_var)
         if val and os.path.isdir(val):
             return val
 
-    # Standard paths
+    # Standard per-platform install paths
-    for path in ("/usr/share/kicad/symbols",):
+    candidates = [
+        # macOS
+        "/Applications/KiCad/KiCad.app/Contents/SharedSupport/symbols",
+        # Linux
+        "/usr/share/kicad/symbols",
+        "/usr/local/share/kicad/symbols",
+        # Windows
+        r"C:\Program Files\KiCad\10.0\share\kicad\symbols",
+        r"C:\Program Files\KiCad\9.0\share\kicad\symbols",
+    ]
+    for path in candidates:
         if os.path.isdir(path):
             return path
 

tests/test_lib_resolver.py

@@ -17,7 +17,6 @@ from mckicad.utils.lib_resolver import (
 )
 from mckicad.utils.sexp_tree import find_recursive, parse
 
-
 # ---------------------------------------------------------------------------
 # Fixtures
 # ---------------------------------------------------------------------------
@@ -69,7 +68,7 @@ def project_with_lib(tmp_path):
         "(sym_lib_table\n"
         "  (version 7)\n"
         '  (lib (name "MyLib")(type "KiCad")'
-        f'(uri "${{KIPRJMOD}}/MyLib.kicad_sym")(options "")(descr ""))\n'
+        '(uri "${KIPRJMOD}/MyLib.kicad_sym")(options "")(descr ""))\n'
         ")\n"
     )
     table_file = tmp_path / "sym-lib-table"
@@ -138,7 +137,7 @@ def multi_unit_lib(tmp_path):
         "(sym_lib_table\n"
         "  (version 7)\n"
         '  (lib (name "OpAmps")(type "KiCad")'
-        f'(uri "${{KIPRJMOD}}/OpAmps.kicad_sym")(options "")(descr ""))\n'
+        '(uri "${KIPRJMOD}/OpAmps.kicad_sym")(options "")(descr ""))\n'
         ")\n"
     )
     (tmp_path / "sym-lib-table").write_text(table_content)
@@ -368,6 +367,17 @@ class TestGetKicadSymbolDir:
         assert os.path.isfile(os.path.join(sym_dir, "Device.kicad_sym"))
 
     def test_env_override(self, tmp_path, monkeypatch):
+        # Clear any ambient symbol-dir vars so the override under test is the
+        # only candidate (a real KICAD_SYMBOL_DIR or install path would
+        # otherwise take precedence).
+        for var in (
+            "KICAD_SYMBOL_DIR",
+            "KICAD10_SYMBOL_DIR",
+            "KICAD9_SYMBOL_DIR",
+            "KICAD8_SYMBOL_DIR",
+            "KICAD7_SYMBOL_DIR",
+        ):
+            monkeypatch.delenv(var, raising=False)
         monkeypatch.setenv("KICAD9_SYMBOL_DIR", str(tmp_path))
         sym_dir = get_kicad_symbol_dir()
         assert sym_dir == str(tmp_path)