ICU-21149 Adding a helper to allow simpler debugging of mappers.

diff --git a/tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/DebugWriter.java b/tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/DebugWriter.java
new file mode 100644 (file)
index 0000000..72994e1
--- /dev/null
+++ b/tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/DebugWriter.java
@@ -0,0 +1,138 @@
+package org.unicode.icu.tool.cldrtoicu;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collection;
+import java.util.function.Function;
+import java.util.logging.Formatter;
+import java.util.logging.LogManager;
+import java.util.logging.LogRecord;
+
+import org.unicode.cldr.api.CldrDataSupplier;
+
+import com.google.common.base.CharMatcher;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableList;
+import com.google.common.io.CharStreams;
+
+/**
+ * Utility to allow any "mapper" class to trivially support a main method and useful
+ * logging behaviour to help avoid the need for ad-hoc logging via {@code System.out}.
+ *
+ * <p>In most cases a mapping class can just have a {@code main} method like:
+ * <pre>{@code
+ *   // Arguments: <output-dir> [<log-level>]
+ *   public static void main(String[] args) throws IOException {
+ *       DebugWriter.writeForDebugging(args, MapperClass::process);
+ *   }
+ * }</pre>
+ *
+ * <p>Note however that running this still requires that the {@code CLDR_DIR} system
+ * property is set.
+ */
+public final class DebugWriter {
+    private static final String PACKAGE_ROOT = "org.unicode.icu.tool.cldrtoicu";
+    private static final String PACKAGE_PREFIX = PACKAGE_ROOT + ".";
+
+    /**
+     * Writes the IcuData generated by the given function using the default {@code CLDR_DIR}
+     * system property.
+     *
+     * <p>This is a helper method to make it easy for each mapper to have its own main
+     * method for debugging, and it should not be used directly by {@code LdmlConverter}.
+     */
+    public static void writeForDebugging(String[] args, Function<CldrDataSupplier, IcuData> fn)
+            throws IOException {
+        writeMultipleForDebugging(args, src -> ImmutableList.of(fn.apply(src)));
+    }
+
+    /**
+     * Writes the IcuData generated by the given function using the default {@code CLDR_DIR}
+     * system property.
+     *
+     * <p>This is a helper method to make it easy for each mapper to have its own main
+     * method for debugging, and it should not be used directly by {@code LdmlConverter}.
+     */
+    public static void writeMultipleForDebugging(
+            String[] args, Function<CldrDataSupplier, Collection<IcuData>> fn)
+            throws IOException {
+        String cldrPath = System.getProperty("CLDR_DIR", System.getenv("CLDR_DIR"));
+        checkState(cldrPath != null,
+                "required 'CLDR_DIR' system property or environment variable not set");
+        checkArgument(args.length >= 1, "expected output directory");
+        Path outDir = Paths.get(args[0]);
+        String logLevel = (args.length == 2) ? args[1] : "OFF";
+
+        String loggerConfig = Joiner.on("\n").join(
+                "handlers = java.util.logging.ConsoleHandler",
+                "java.util.logging.ConsoleHandler.level     = ALL",
+                "java.util.logging.ConsoleHandler.encoding  = UTF-8",
+                "java.util.logging.ConsoleHandler.formatter = " + LogFormatter.class.getName(),
+                "",
+                PACKAGE_ROOT + ".level  = " + logLevel);
+        LogManager.getLogManager()
+                .readConfiguration(new ByteArrayInputStream(loggerConfig.getBytes(UTF_8)));
+
+        Files.createDirectories(outDir);
+        CldrDataSupplier src = CldrDataSupplier.forCldrFilesIn(Paths.get(cldrPath));
+        ImmutableList<String> header = readLinesFromResource("/ldml2icu_header.txt");
+        for (IcuData icuData : fn.apply(src)) {
+            IcuTextWriter.writeToFile(icuData, outDir, header, true);
+        }
+    }
+
+    private static ImmutableList<String> readLinesFromResource(String name) {
+        try (InputStream in = DebugWriter.class.getResourceAsStream(name)) {
+            return ImmutableList.copyOf(CharStreams.readLines(new InputStreamReader(in, UTF_8)));
+        } catch (IOException e) {
+            throw new RuntimeException("cannot read resource: " + name, e);
+        }
+    }
+
+    // Format is "<localClass>#<plainMethod>: <message>" since this is a fairly
+    // small code base and keeping logs concise is helpful.
+    // This is only public because it has to be reflectively instantiated.
+    public static final class LogFormatter extends Formatter {
+        private static final CharMatcher SEPARATORS = CharMatcher.anyOf("$#");
+
+        @Override
+        public String format(LogRecord logRecord) {
+            String message = String.format("%s#%s: %s\n",
+                    localClassName(logRecord.getSourceClassName()),
+                    plainMethodName(logRecord.getSourceMethodName()),
+                    logRecord.getMessage());
+            if (logRecord.getThrown() != null) {
+                message += logRecord.getThrown() + "\n";
+            }
+            return message;
+        }
+
+        // Since everything is in the same base package, elide that (if present).
+        private String localClassName(String className) {
+            return className.startsWith(PACKAGE_PREFIX)
+                    ? className.substring(className.lastIndexOf(".") + 1)
+                    : className;
+        }
+
+        // Trim method names to remove things like lambda prefixes and anonymous
+        // class suffixes (these add noise to every log and aren't that useful).
+        private String plainMethodName(String methodName) {
+            if (methodName.startsWith("lambda$")) {
+                methodName = methodName.substring("lambda$".length());
+            }
+            if (SEPARATORS.matchesAnyOf(methodName)) {
+                methodName = methodName.substring(0, SEPARATORS.indexIn(methodName));
+            }
+            return methodName;
+        }
+    }
+}