fix(builder): strip UTF-8 BOM from .ino sources before preprocessing #2983

Original file line number	Diff line number	Diff line change
Expand Up		@@ -37,6 +37,14 @@ var (
		includesArduinoH = regexp.MustCompile(`(?m)^\s#\sinclude\s*[<\"]Arduino\.h[>\"]`)
		)

	// stripUTF8BOM removes a UTF-8 BOM if present at the start of the file.
	func stripUTF8BOM(b []byte) []byte {
	if len(b) >= 3 && b[0] == 0xEF && b[1] == 0xBB && b[2] == 0xBF {
	return b[3:]
	}
	return b
	}

		// prepareSketchBuildPath copies the sketch source files in the build path.
		// The .ino files are merged together to create a .cpp file (by the way, the
		// .cpp file still needs to be Arduino-preprocessed to compile).
Expand Down Expand Up		@@ -82,6 +90,7 @@ func (b *Builder) sketchMergeSources(overrides map[string]string) (int, string,
		if err != nil {
		return "", errors.New(i18n.Tr("reading file %[1]s: %[2]s", f, err))
		}
	data = stripUTF8BOM(data)
		return string(data), nil
		}

Expand Down Expand Up		@@ -136,7 +145,9 @@ func (b Builder) sketchCopyAdditionalFiles(buildPath paths.Path, overrides map
		if err != nil {
		return fmt.Errorf("%s: %w", i18n.Tr("unable to read contents of the source item"), err)
		}
	s = stripUTF8BOM(s)
		sourceBytes = s

		}

		// tag each additional file with the filename of the source it was copied from
Expand Down

19 changes: 19 additions & 0 deletions internal/arduino/builder/sketch_test.go

Show comments View file Open in desktop

Original file line number	Diff line number	Diff line change
Expand Up		@@ -106,3 +106,22 @@ func TestCopyAdditionalFiles(t *testing.T) {
		require.NoError(t, err)
		require.Equal(t, info1.ModTime(), info2.ModTime())
		}

	func TestStripUTF8BOM(t *testing.T) {
	// Case 1: Input with BOM
	inputWithBOM := []byte{0xEF, 0xBB, 0xBF, 'H', 'e', 'l', 'l', 'o'}
	expected := []byte("Hello")

	output := stripUTF8BOM(inputWithBOM)
	require.Equal(t, expected, output, "BOM should be stripped")

	// Case 2: Input without BOM
	inputNoBOM := []byte("Hello")
	outputNoBOM := stripUTF8BOM(inputNoBOM)
	require.Equal(t, inputNoBOM, outputNoBOM, "Input without BOM should remain unchanged")

	// Case 3: Input shorter than 3 bytes (edge case)
	shortInput := []byte{0xEF}
	outputShort := stripUTF8BOM(shortInput)
	require.Equal(t, shortInput, outputShort, "Short input should remain unchanged")
	}

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