fix(parse): report draw operations that use an undefined aperture

CHANGELOG.md

@@ -9,6 +9,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **Draw operations using an undefined aperture are no longer dropped in
+  silence** ([#17]) -- selecting a D-code that was never defined (or drawing
+  before any `Dnn` selection at all) left the flash or stroke carrying an
+  aperture index with no definition behind it.  Every consumer treated that
+  as nothing to draw: both geometry emit helpers returned early and the
+  raster renderer drew nothing, with no diagnostic at any severity.  `diff`
+  and `geomdiff` then reported `0 changes` at exit `0`, and the JSON report
+  was byte-identical to a comparison of two genuinely identical boards -- so
+  a real fabrication change could pass a `--fail-on-diff` gate invisibly.
+  The parser now emits an `Error` diagnostic at the offending draw
+  operation, which the existing promotion path turns into exit `2` for
+  `parse`, `render`, `diff` and `geomdiff` alike.  D02 moves and G36/G37
+  region contours consume no aperture and are unaffected.
+
 - **Degenerate region contours no longer leak line geometry** -- a G36/G37
   contour whose points are collinear produced a zero-area `MultiLineString`
   from `make_valid` that flowed into the geometry engine; region expansion
@@ -671,6 +685,7 @@ merge_tolerance) -> SingleLayerDiff`.
 - mypy `strict=true`, `warn_unused_ignores=true`, `cairocffi.*` override for missing stubs.
 - 2 smoke tests in `tests/test_scaffold.py`.
 
+[#17]: https://github.com/heibench/gerberdiff/issues/17
 [Unreleased]: https://github.com/heibench/gerberdiff/compare/v0.29.1...HEAD
 [0.29.1]: https://github.com/heibench/gerberdiff/compare/v0.29.0...v0.29.1
 [0.29.0]: https://github.com/heibench/gerberdiff/compare/9ffd4c8f...v0.29.0

gerberdiff/parse/gerber_state.py

@@ -163,6 +163,10 @@ def __init__(self, source_path: Path | None) -> None:
         self._net_attrs: dict[str, str] = {}
         self._aperture_attrs: dict[str, str] = {}
 
+        # Offending D-codes already reported, so one bad aperture used by
+        # thousands of flashes yields one diagnostic rather than thousands.
+        self._undefined_apertures: set[int] = set()
+
         # ---- block aperture stack ----
         # Each frame saves state so that when %AB*% closes the block the
         # parent drawing context is fully restored.
@@ -241,7 +245,28 @@ def _reset_block(self) -> None:
     # Net emission
     # ------------------------------------------------------------------
 
-    def _emit_net(self) -> None:
+    def _check_aperture_defined(self, line: int) -> None:
+        """Error when the op about to be emitted would draw with no aperture.
+
+        Region contours are filled from their outline and D02 only moves the
+        cursor, so neither consumes an aperture.  Every other op does, and a
+        missing definition means the geometry is dropped -- silently, before
+        this check existed.
+        """
+        if self._in_region_fill or self._aperture_state == ApertureState.Off:
+            return
+        code = self._current_aperture
+        if code in self._apertures or code in self._undefined_apertures:
+            return
+        self._undefined_apertures.add(code)
+        if code == 0:
+            self._error("Draw operation before any aperture was selected", line)
+        else:
+            self._error(f"Draw operation uses undefined aperture D{code}", line)
+
+    def _emit_net(self, line: int) -> None:
+        self._check_aperture_defined(line)
+
         fmt = self._fmt
 
         # Resolve stop position (use prev if coordinate not updated this block)
@@ -736,7 +761,7 @@ def parse(self, content: str) -> ParsedImage:
 
             elif tt == TokenType.END_OF_BLOCK:
                 if self._coord_changed:
-                    self._emit_net()
+                    self._emit_net(line)
                 self._reset_block()
 
             elif tt == TokenType.EXTENDED:

tests/test_cli_diff.py

@@ -260,3 +260,24 @@ def test_diff_removed_layer_reports_correctly(tmp_path: Path) -> None:
     )
     result = _run("diff", str(before), str(after), "--width", "64", "--height", "64")
     assert result.exit_code == 0, result.output
+
+
+# ---------------------------------------------------------------------------
+# Undefined apertures (issue #17)
+# ---------------------------------------------------------------------------
+
+
+def test_diff_undefined_aperture_fails_the_gate(tmp_path: Path) -> None:
+    """The raster engine drops the flash too -- it must not report 0 changes."""
+    before, after = tmp_path / "b", tmp_path / "a"
+    header = "%FSLAX26Y26*%\n%MOIN*%\n"
+    good = header + "%ADD10C,0.1*%\nD10*\nX0Y0D03*\n" + "M02*\n"
+    before.mkdir()
+    after.mkdir()
+    (before / "board-F.Cu.gbr").write_text(good)
+    (after / "board-F.Cu.gbr").write_text(
+        header + "%ADD10C,0.1*%\nD10*\nX0Y0D03*\nD11*\nX500000Y500000D03*\n" + "M02*\n"
+    )
+    result = _run("diff", str(before), str(after), "--fail-on-diff")
+    assert result.exit_code == 2, result.output
+    assert "undefined aperture D11" in result.output

tests/test_cli_geomdiff.py

@@ -180,3 +180,30 @@ def test_geomdiff_parse_error_exit_2(tmp_path: Path) -> None:
     result = _run("geomdiff", str(before), str(after))
     assert result.exit_code == 2
     assert "error" in result.output.lower()
+
+
+# ---------------------------------------------------------------------------
+# Undefined apertures (issue #17)
+# ---------------------------------------------------------------------------
+
+
+def _write_board_with_undefined_aperture(directory: Path) -> None:
+    """The same pad, plus a second flash on a D-code that is never defined."""
+    directory.mkdir(parents=True, exist_ok=True)
+    src = _HEADER + "%ADD10C,0.1*%\nD10*\nX0Y0D03*\n" + "D11*\nX500000Y500000D03*\n" + _FOOTER
+    (directory / "board-F.Cu.gbr").write_text(src)
+
+
+def test_geomdiff_undefined_aperture_fails_the_gate(tmp_path: Path) -> None:
+    """An added pad on an undefined aperture must not read as "no changes".
+
+    The flash is dropped from the geometry, so before this was reported the
+    comparison came back 0 changes at exit 0 and a real fabrication change
+    passed the gate invisibly.
+    """
+    _write_board(tmp_path / "b", 0)
+    _write_board_with_undefined_aperture(tmp_path / "a")
+    result = _run("geomdiff", str(tmp_path / "b"), str(tmp_path / "a"), "--fail-on-diff")
+    assert result.exit_code == 2, result.output
+    assert "undefined aperture D11" in result.output
+    assert "0 changes" not in result.output

tests/test_gerber_state.py

@@ -12,8 +12,10 @@
 
 
 def test_parse_minimal() -> None:
-    # FSLAX25Y25, MOMM unit, circle D10, linear draw, end
-    content = "%FSLAX25Y25*%%MOMM*%%ADD10C,1.0*%G01*X100000Y100000D01*M02*"
+    # FSLAX25Y25, MOMM unit, circle D10, select it, linear draw, end.
+    # The D10* selection is load-bearing: without it the stroke carries
+    # aperture 0, which is undefined, and expands to no geometry at all.
+    content = "%FSLAX25Y25*%%MOMM*%%ADD10C,1.0*%D10*G01*X100000Y100000D01*M02*"
     img = parse_gerber(content)
     assert img.bounding_box.is_valid
     assert len(img.draw_ops) > 0
@@ -416,3 +418,67 @@ def test_sr_parse_records_step_and_repeat_on_layer() -> None:
     assert sr.y == 2
     assert abs(sr.dist_x - 1.0) < 1e-9
     assert abs(sr.dist_y - 0.5) < 1e-9
+
+
+# ---------------------------------------------------------------------------
+# Undefined apertures (issue #17)
+#
+# A draw op whose aperture was never defined is dropped by every downstream
+# consumer -- both geometry emit helpers and the raster renderer treat a
+# missing aperture as "nothing to draw".  Before the parser reported it, a
+# real fabrication change could pass a --fail-on-diff gate at exit 0.
+# ---------------------------------------------------------------------------
+
+_HDR = "%FSLAX26Y26*%\n%MOIN*%\n"
+
+
+def _errors(gerber: str) -> list[str]:
+    img = parse_gerber(gerber)
+    return [d.message for d in img.diagnostics if d.severity == DiagnosticSeverity.Error]
+
+
+def test_flash_with_undefined_aperture_is_an_error() -> None:
+    errs = _errors(_HDR + "D11*\nX1000Y1000D03*\nM02*\n")
+    assert errs == ["Draw operation uses undefined aperture D11"]
+
+
+def test_stroke_with_undefined_aperture_is_an_error() -> None:
+    errs = _errors(_HDR + "D11*\nX0Y0D02*\nX1000Y1000D01*\nM02*\n")
+    assert errs == ["Draw operation uses undefined aperture D11"]
+
+
+def test_flash_before_any_aperture_is_selected_is_an_error() -> None:
+    """No D-code at all leaves _current_aperture at 0, which is also undefined."""
+    errs = _errors(_HDR + "X1000Y1000D03*\nM02*\n")
+    assert errs == ["Draw operation before any aperture was selected"]
+
+
+def test_undefined_aperture_error_carries_the_line_of_the_draw_op() -> None:
+    img = parse_gerber(_HDR + "%ADD10C,0.1*%\nD10*\nX0Y0D03*\nD11*\nX1000Y1000D03*\nM02*\n")
+    errs = [d for d in img.diagnostics if d.severity == DiagnosticSeverity.Error]
+    assert len(errs) == 1
+    # Line 7 is the flash, not line 6 where D11 was selected.
+    assert errs[0].line == 7
+
+
+def test_move_with_undefined_aperture_is_not_an_error() -> None:
+    """D02 only repositions the cursor -- it consumes no aperture."""
+    assert _errors(_HDR + "D11*\nX1000Y1000D02*\nM02*\n") == []
+
+
+def test_region_fill_needs_no_aperture() -> None:
+    """G36/G37 contours are filled from their outline, so none is selected."""
+    gerber = _HDR + "G36*\nX0Y0D02*\nX1000Y0D01*\nX1000Y1000D01*\nX0Y0D01*\nG37*\nM02*\n"
+    assert _errors(gerber) == []
+
+
+def test_defined_aperture_draws_without_error() -> None:
+    """Guard against the check firing on every file."""
+    assert _errors(_HDR + "%ADD10C,0.1*%\nD10*\nX1000Y1000D03*\nM02*\n") == []
+
+
+def test_undefined_aperture_is_reported_once_per_code() -> None:
+    """One bad aperture used by many flashes must not emit one error each."""
+    body = "".join(f"X{i * 100}Y0D03*\n" for i in range(200))
+    errs = _errors(_HDR + "D11*\n" + body + "M02*\n")
+    assert errs == ["Draw operation uses undefined aperture D11"]