Change print_record() Fix function prefix parameter to format string. (#238)

Author: blackwinter

README.md

@@ -311,7 +311,7 @@ Prints the current record as JSON either to standard output or to a file.
 
 Parameters:
 
-- `prefix` (optional): Prefix to print before the record. (Default: Empty string)
+- `prefix` (optional): Prefix to print before the record; may include [format directives](https://docs.oracle.com/javase/8/docs/api/java/util/Formatter.html#syntax) for counter and record ID (in that order). (Default: Empty string)
 
 Options:
 
@@ -320,7 +320,7 @@ Options:
 - `encoding` (file output only): Encoding used by the underlying writer. (Default: `UTF-8`)
 - `footer`: Footer which is output after the record. (Default: `\n`)
 - `header`: Header which is output before the record. (Default: Empty string)
-- `id`: Field name which contains the record ID; if found, will be included before the prefix. (Default: `_id`)
+- `id`: Field name which contains the record ID; if found, will be available for inclusion in `prefix` and `destination`. (Default: `_id`)
 - `pretty`: Whether to use pretty printing. (Default: `false`)
 
 ```perl
@@ -330,7 +330,7 @@ print_record(["<prefix>"][, <options>...])
 E.g.:
 
 ```perl
-print_record("Before transformation")
+print_record("%d) Before transformation: ")
 print_record(destination: "record-%2$s.json", id: "001", pretty: "true")
 print_record(destination: "record-%03d.json.gz", header: "After transformation: ")
 ```

metafix/src/main/java/org/metafacture/metafix/FixMethod.java

@@ -224,12 +224,11 @@ public void apply(final Metafix metafix, final Record record, final List<String>
 
             final boolean pretty = getBoolean(options, "pretty");
 
-            final String id = Value.isNull(idValue) ? "" : idValue.toString();
-            final String prefix = (id.isEmpty() ? "" : "[" + id + "] ") + (params.isEmpty() ? "" : params.get(0) + ": ");
-
             final LongAdder counter = scopedCounter.computeIfAbsent(metafix, k -> new LongAdder());
             counter.increment();
 
+            final String id = Value.isNull(idValue) ? "" : idValue.toString();
+            final String prefix = params.isEmpty() ? "" : String.format(params.get(0), counter.sum(), id);
             final ObjectWriter<String> writer = new ObjectWriter<>(String.format(destination, counter.sum(), id));
 
             withOption(options, "compression", writer::setCompression);