MPS 2018.1 Help

Code completion

This section covers various techniques of context-aware code completion that allow you to speed up the coding process.

Basic completion: names and keywords

Basic code completion helps you complete the names of classes, methods, and keywords within the visibility scope. When you invoke code completion, MPS analyses the context and suggests the choices that are reachable from the current caret position.

If basic code completion is applied to part of a parameter, or a variable declaration, MPS suggests a list of possible names depending on the item type.

Invoke basic completion

  1. Start typing a name.
  2. Press N/A or choose Code | Completion | Basic from the main menu.
  3. If necessary, press N/A for the second time (this action has the same effect as pressing N/A).

Smart completion based on type

Smart code completion filters the suggestions list and shows only the types applicable to the current context.

Invoke smart completion

  1. Start typing.
  2. Press N/A.

    The most suitable suggestion for the current context is highlighted.

  3. If necessary, press N/A once again.

Statements completion

Statements completion enables you to create syntactically correct code constructs. It inserts the necessary syntax elements (parentheses, braces, semicolons etc.) and gets you in a position where you can start typing the next statement.

Complete a statement

  • Start typing a statement. The punctuation required in the current context is added automatically, and the caret moves to the next editing position.

Complete a code construct

  • Start typing a code construct and press N/A:

    MPS automatically completes the construct, and the caret is placed at the next editing position:

Hippie completion: expanding words based on context

Hippie completion is a completion engine that analyses your text in the visible scope and draws suggestions from the current context. It helps you complete a word with a keyword, class name, method or variable.

Expand a string at caret to an existing word

  1. Type the initial string and do one of the following:
    • Press N/A or choose Code | Completion | Cyclic Expand Word to search for matching words before the caret
    • Press N/A or choose Code | Completion | Cyclic Expand Word (Backward) to search for matching words after the caret and in other open files.
    The first suggested value appears, and the prototype is highlighted in the source code:
  2. Press N/A to accept the suggestion, or hold the Alt key and keep pressing Slash until the desired word is found.

Postfix code completion

Postfix code completion helps you reduce backward caret jumps as you write code. It allows you to transform an already typed expression to a different one based on a postfix you type after the dot, the type of expression, and its context.

Transform a statement with a postfix

  • Type an expression and then type a postfix after a dot, for example .if:
    function m(arg) { arg.if }

    The initial expression gets wrapped with an if statement:

    function m(arg) { if (arg) { } }

To disable certain postfix completion templates, in the Settings/Preferences dialog (N/A) select Editor | General | Postfix Completion. You can also choose which key you want to use to expand postfix templates: Tab, Space, or Enter.

You can edit the predefined postfix templates, for example to replace a long key with a shorter one, or to expand the list of expression types it's applicable to.

Configure code completion settings

Configure completion options

  1. In the Settings/Preferences dialog (N/A) select Editor | General | Code Completion.
  2. Do the following:
    • To automatically display the suggestions list without having to call code completion explicitly by pressing N/A for basic completion or N/A for smart completion, select the Auto-display code completion checkbox.

      You can also choose to automatically insert suggestions when there's just one option: select the completion type under Auto-insert when only one choice on.

    • To sort suggestions in the alphabetical order, instead of sorting them by relevance, select the Sort lookup items lexicographically checkbox.

      You can also toggle these modes by clicking a icon or pi icon respectively in the lower-right corner of the list.

    • If you want case to be taken into account when suggesting completion options, select one of the options next to Case sensitive completion.
    • If you want the documentation popup up to be displayed automatically, select the Auto-display documentation option. Note that this is only valid if automatic completion is disabled and you invoke it explicitly.

Completion tips and tricks

Narrow down the suggestions list

You can narrow down the suggestions list by typing any part of a word (even characters from somewhere in the middle), or invoking code completion after a dot separator. MPS will show suggestions that include the characters you've entered in any positions.

This makes the use of wildcards unnecessary:

In case of CamelCase or snake_case names, type the initial letters only. MPS automatically recognizes and matches the initial letters.

Accept a suggestion

You can accept a suggestion from the list in one of the following ways:

  • Press N/A or double-click a list item to insert it to the left of the caret.
  • Press N/A to replace the characters to the right from the caret.
  • Use N/A to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, etc.)

You can also use specific keys to insert the selected completion suggestion: in the Settings/Preferences dialog (N/A) choose Editor | General | Code Completion and select the Insert selected variant by dyping dot, space, etc. option. These keys depend on the language, your context, etc.

View reference information

  • You can use the Quick Definition View by pressing N/A when you select an entry in the suggestions list:

View code hierarchy

You can view code hierarchy when you've selected an entry from the suggestions list:

  • N/A: view type hierarchy
  • N/A: view method hierarchy.

Troubleshooting

If code completion doesn't work, this may be due to one of the following reasons:

  • The Power Save Mode is on (File | Power Save Mode). Turning it on minimizes power consumption of your laptop by eliminating the background operations, including error highlighting, on-the-fly inspections, and code completion.
  • An SDK is not configured for your project.
  • Your file doesn't reside in a content root and is not bound to a build path, so it doesn't get the required class definitions and resources needed for code completion.
  • A file containing classes and functions that you want to appear in completion suggestions list is marked as a plain text file.
  • External libraries that contain functions that you want to appear in completion suggestions list are not added as dependencies or global libraries.
Last modified: 4 April 2018