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92 lines
2.5 KiB
Markdown
92 lines
2.5 KiB
Markdown
---
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layout: editable
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title: Grammar and Parser
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---
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### 1. Define a token type
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```java
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package com.simpleplugin.psi;
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import com.intellij.psi.tree.IElementType;
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import com.simpleplugin.SimpleLanguage;
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import org.jetbrains.annotations.NonNls;
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import org.jetbrains.annotations.NotNull;
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public class SimpleTokenType extends IElementType {
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public SimpleTokenType(@NotNull @NonNls String debugName) {
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super(debugName, SimpleLanguage.INSTANCE);
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}
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@Override
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public String toString() {
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return "SimpleTokenType." + super.toString();
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}
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}
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```
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### 2. Define an element type
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```java
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package com.simpleplugin.psi;
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import com.intellij.psi.tree.IElementType;
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import com.simpleplugin.SimpleLanguage;
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import org.jetbrains.annotations.NonNls;
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import org.jetbrains.annotations.NotNull;
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public class SimpleElementType extends IElementType {
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public SimpleElementType(@NotNull @NonNls String debugName) {
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super(debugName, SimpleLanguage.INSTANCE);
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}
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}
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```
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### 3. Define grammar
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Define a grammar for the properties language with */com/simpleplugin/Simple.bnf* file.
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```java
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{
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parserClass="com.simpleplugin.parser.SimpleParser"
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extends="com.intellij.extapi.psi.ASTWrapperPsiElement"
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psiClassPrefix="Simple"
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psiImplClassSuffix="Impl"
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psiPackage="com.simpleplugin.psi"
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psiImplPackage="com.simpleplugin.psi.impl"
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elementTypeHolderClass="com.simpleplugin.psi.SimpleTypes"
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elementTypeClass="com.simpleplugin.psi.SimpleElementType"
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tokenTypeClass="com.simpleplugin.psi.SimpleTokenType"
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}
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simpleFile ::= item_*
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private item_ ::= (property|COMMENT|CRLF)
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property ::= (KEY? SEPARATOR VALUE?) | KEY
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```
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As you see a properties file can contain properties, comments and line breaks.
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The grammar defines how flexible the support for a language can be.
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We specified that a property may have or may not have key and value.
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This lets the IDE still recognise incorrectly defined properties and provide corresponding code analysis and quick-fixes.
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### 4. Generate a parser
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Now when the grammar is defined we can generate a parser with PSI classes via *Generate Parser Code* from the context menu or via *⌘⇧G* shortcut on *Simple.bnf* file.
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The Grammar-Kit will generate a parser and PSI elements in *gen* folder.
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Mark this folder as a source root and make sure everything is compiled without errors.
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-------
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[Previous](language_and_filetype.html)
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[Top](cls_tutorial.html)
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[Next](lexer_and_parser_definition.html)
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