Gracefully skip parsing errors when source files use unsupported encoding

plugin/src/main/java/io/jenkins/plugins/coverage/metrics/source/SourceCodePainter.java

@@ -8,11 +8,15 @@
 import edu.hm.hafner.util.FilteredLog;
 import edu.umd.cs.findbugs.annotations.NonNull;
 
+import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.IOException;
 import java.io.Serial;
+import java.io.InputStreamReader;
+import java.nio.charset.CodingErrorAction;
 import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
 import java.nio.file.Path;
@@ -213,8 +217,8 @@ private int paint(final CoverageSourcePrinter paint, final String relativePathId
             try {
                 Path paintedFilesFolder = Files.createTempDirectory(temporaryFolder, directory);
                 var fullSourcePath = paintedFilesFolder.resolve(sanitizedFileName);
-                try (BufferedWriter output = Files.newBufferedWriter(fullSourcePath)) {
-                    List<String> lines = Files.readAllLines(Path.of(resolvedPath.getRemote()), charset);
+                try (BufferedWriter output = Files.newBufferedWriter(fullSourcePath, StandardCharsets.UTF_8)) {
+                    List<String> lines = readSourceLines(Path.of(resolvedPath.getRemote()), charset);
 
                     // added a header to display what is being shown in each column
                     output.write(paint.getColumnHeader());
@@ -233,6 +237,14 @@ private int paint(final CoverageSourcePrinter paint, final String relativePathId
             }
         }
 
+        private List<String> readSourceLines(final Path sourcePath, final Charset charset) throws IOException {
+            try (var reader = new BufferedReader(new InputStreamReader(Files.newInputStream(sourcePath),
+                    charset.newDecoder().onMalformedInput(CodingErrorAction.REPLACE)
+                            .onUnmappableCharacter(CodingErrorAction.REPLACE)))) {
+                return reader.lines().collect(Collectors.toList());
+            }
+        }
+
         private Optional<FilePath> findSourceFile(final FilePath workspace, final String fileName,
                 final FilteredLog log) {
             try {

plugin/src/test/java/io/jenkins/plugins/coverage/metrics/source/SourceCodePainterTest.java

@@ -0,0 +1,96 @@
+package io.jenkins.plugins.coverage.metrics.source;
+
+import org.junit.jupiter.api.Test;
+
+import edu.hm.hafner.coverage.FileNode;
+import edu.hm.hafner.util.FilteredLog;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Verifies that source painting handles files with extended ASCII characters.
+ *
+ * @author Akash Manna
+ */
+class SourceCodePainterTest {
+    private static final Charset WINDOWS_1252 = Charset.forName("windows-1252");
+
+    @Test
+    void shouldPaintSourceFilesWithExtendedAsciiCharacters() throws IOException, InterruptedException {
+        Path workspace = Files.createTempDirectory("source-painter");
+        Path sourceFile = workspace.resolve("Example.m");
+
+        Files.write(sourceFile, List.of(
+                "function y = example()",
+                "% Copyright 2026, Café Corporation",
+                "y = 1;"), WINDOWS_1252);
+
+        var painter = new SourceCodePainter.AgentCoveragePainter(
+                List.of(new CoverageSourcePrinter(new FileNode("", "Example.m"))),
+                "windows-1252",
+                "coverage");
+
+        FilteredLog log = painter.invoke(workspace.toFile(), null);
+
+        assertThat(log.getErrorMessages()).isEmpty();
+        assertThat(log.getInfoMessages()).contains("-> finished painting successfully");
+
+        Path outerZipPath = workspace.resolve(SourceCodeFacade.COVERAGE_SOURCES_ZIP);
+        assertThat(outerZipPath).exists();
+
+        byte[] paintedBytes = readPaintedBytesFromNestedZip(outerZipPath);
+
+        var renderedText = new String(paintedBytes, StandardCharsets.UTF_8).replace("\u00A0", " ");
+        assertThat(renderedText).contains("Copyright 2026, Café Corporation");
+    }
+
+    private byte[] readPaintedBytesFromNestedZip(final Path outerZipPath) throws IOException {
+        try (var outerZip = new ZipInputStream(Files.newInputStream(outerZipPath))) {
+            ZipEntry outerEntry = outerZip.getNextEntry();
+
+            while (outerEntry != null) {
+                if (outerEntry.getName().endsWith(SourceCodeFacade.ZIP_FILE_EXTENSION)) {
+                    byte[] innerZipBytes = outerZip.readAllBytes();
+                    byte[] content = extractBytesFromZip(innerZipBytes);
+
+                    if (content.length > 0) {
+                        return content;
+                    }
+                }
+
+                outerEntry = outerZip.getNextEntry();
+            }
+        }
+
+        return new byte[0];
+    }
+
+    private byte[] extractBytesFromZip(final byte[] zipBytes) throws IOException {
+        var out = new ByteArrayOutputStream();
+
+        try (var innerZip = new ZipInputStream(new ByteArrayInputStream(zipBytes))) {
+            ZipEntry entry = innerZip.getNextEntry();
+
+            while (entry != null) {
+                if (!entry.isDirectory()) {
+                    out.write(innerZip.readAllBytes());
+                }
+
+                entry = innerZip.getNextEntry();
+            }
+        }
+
+        return out.toByteArray();
+    }
+}