repl: add support for custom completions

Allow user code to override the default `complete()` function from
`readline.Interface`. See:
https://nodejs.org/api/readline.html#readline_use_of_the_completer_function

Ref: nodejs/node-v0.x-archive#8484

PR-URL: #7527
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Lance Ball <lball@redhat.com>

doc/api/repl.md

@@ -382,6 +382,8 @@ added: v0.1.91
      `undefined`. Defaults to `false`.
   * `writer` {Function} The function to invoke to format the output of each
      command before writing to `output`. Defaults to [`util.inspect()`][].
+  * `completer` {Function} An optional function used for custom Tab auto
+     completion. See [`readline.InterfaceCompleter`][] for an example.
   * `replMode` - A flag that specifies whether the default evaluator executes
     all JavaScript commands in strict mode, default mode, or a hybrid mode
     ("magic" mode.) Acceptable values are:
@@ -526,3 +528,4 @@ see: https://gist.github.com/2053342
 [`util.inspect()`]: util.html#util_util_inspect_object_options
 [here]: util.html#util_custom_inspect_function_on_objects
 [`readline.Interface`]: readline.html#readline_class_interface
+[`readline.InterfaceCompleter`]: readline.html#readline_use_of_the_completer_function

lib/repl.js

@@ -386,14 +386,15 @@ function REPLServer(prompt,
   self.bufferedCommand = '';
   self.lines.level = [];
 
-  function complete(text, callback) {
-    self.complete(text, callback);
-  }
+  // Figure out which "complete" function to use.
+  self.completer = (typeof options.completer === 'function')
+    ? options.completer
+    : complete;
 
   Interface.call(this, {
     input: self.inputStream,
     output: self.outputStream,
-    completer: complete,
+    completer: self.completer,
     terminal: options.terminal,
     historySize: options.historySize,
     prompt
@@ -698,6 +699,10 @@ function filteredOwnPropertyNames(obj) {
   return Object.getOwnPropertyNames(obj).filter(intFilter);
 }
 
+REPLServer.prototype.complete = function() {
+  this.completer.apply(this, arguments);
+};
+
 // Provide a list of completions for the given leading text. This is
 // given to the readline interface for handling tab completion.
 //
@@ -708,7 +713,7 @@ function filteredOwnPropertyNames(obj) {
 //
 // Warning: This eval's code like "foo.bar.baz", so it will run property
 // getter code.
-REPLServer.prototype.complete = function(line, callback) {
+function complete(line, callback) {
   // There may be local variables to evaluate, try a nested REPL
   if (this.bufferedCommand !== undefined && this.bufferedCommand.length) {
     // Get a new array of inputed lines
@@ -967,7 +972,7 @@ REPLServer.prototype.complete = function(line, callback) {
 
     callback(null, [completions || [], completeOn]);
   }
-};
+}
 
 
 /**

test/parallel/test-repl-tab-complete.js

@@ -32,7 +32,7 @@ testMe.complete('console.lo', common.mustCall(function(error, data) {
   assert.deepStrictEqual(data, [['console.log'], 'console.lo']);
 }));
 
-// Tab Complete will return globaly scoped variables
+// Tab Complete will return globally scoped variables
 putIn.run(['};']);
 testMe.complete('inner.o', common.mustCall(function(error, data) {
   assert.deepStrictEqual(data, works);
@@ -283,3 +283,68 @@ if (typeof Intl === 'object') {
 testNonGlobal.complete('I', common.mustCall((error, data) => {
   assert.deepStrictEqual(data, builtins);
 }));
+
+// To test custom completer function.
+// Sync mode.
+const customCompletions = 'aaa aa1 aa2 bbb bb1 bb2 bb3 ccc ddd eee'.split(' ');
+const testCustomCompleterSyncMode = repl.start({
+  prompt: '',
+  input: putIn,
+  output: putIn,
+  completer: function completerSyncMode(line) {
+    const hits = customCompletions.filter((c) => {
+      return c.indexOf(line) === 0;
+    });
+    // Show all completions if none found.
+    return [hits.length ? hits : customCompletions, line];
+  }
+});
+
+// On empty line should output all the custom completions
+// without complete anything.
+testCustomCompleterSyncMode.complete('', common.mustCall((error, data) => {
+  assert.deepStrictEqual(data, [
+    customCompletions,
+    ''
+  ]);
+}));
+
+// On `a` should output `aaa aa1 aa2` and complete until `aa`.
+testCustomCompleterSyncMode.complete('a', common.mustCall((error, data) => {
+  assert.deepStrictEqual(data, [
+    'aaa aa1 aa2'.split(' '),
+    'a'
+  ]);
+}));
+
+// To test custom completer function.
+// Async mode.
+const testCustomCompleterAsyncMode = repl.start({
+  prompt: '',
+  input: putIn,
+  output: putIn,
+  completer: function completerAsyncMode(line, callback) {
+    const hits = customCompletions.filter((c) => {
+      return c.indexOf(line) === 0;
+    });
+    // Show all completions if none found.
+    callback(null, [hits.length ? hits : customCompletions, line]);
+  }
+});
+
+// On empty line should output all the custom completions
+// without complete anything.
+testCustomCompleterAsyncMode.complete('', common.mustCall((error, data) => {
+  assert.deepStrictEqual(data, [
+    customCompletions,
+    ''
+  ]);
+}));
+
+// On `a` should output `aaa aa1 aa2` and complete until `aa`.
+testCustomCompleterAsyncMode.complete('a', common.mustCall((error, data) => {
+  assert.deepStrictEqual(data, [
+    'aaa aa1 aa2'.split(' '),
+    'a'
+  ]);
+}));