8000 feature #7831 Added an article about ExpressionLanguage AST (javiereg… · symfony/symfony-docs@cf274b7 · GitHub
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feature #7831 Added an article about ExpressionLanguage AST (javiereguiluz)
This PR was squashed before being merged into the 3.2 branch (closes #7831). Discussion ---------- Added an article about ExpressionLanguage AST I need ExpressionLanguage experts to review the first part of the new article and to give me clues about how to write the second part. Thanks! Let's ping some experts in this: @lyrixx and @nicolas-grekas. This fixes #7185. Commits ------- a91a590 Added an article about ExpressionLanguage AST
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‎components/expression_language.rst

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The component provides some different caching strategies, read more about them
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in :doc:`/components/expression_language/caching`.
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AST Dumping and Editing
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-----------------------
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The AST (*Abstract Syntax Tree*) of expressions can be dumped and manipulated
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as explained in :doc:`/components/expression_language/ast`.
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Learn More
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----------
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‎components/expression_language/ast.rst

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.. index::
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single: AST; ExpressionLanguage
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single: AST; Abstract Syntax Tree
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Dumping and Manipulating the AST of Expressions
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===============================================
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Manipulating or inspecting the expressions created with the ExpressionLanguage
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component is difficult because they are plain strings. A better approach is to
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turn those expressions into an AST. In computer science, `AST`_ (*Abstract
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Syntax Tree*) is *"a tree representation of the structure of source code written
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in a programming language"*. In Symfony, a ExpressionLanguage AST is a set of
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nodes that contain PHP classes representing the given expression.
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Dumping the AST
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---------------
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Call the :method:`Symfony\\Component\\ExpressionLanguage\\ExpressionLanguage::getNodes`
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method after parsing any expression to get its AST::
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use Symfony\Component\ExpressionLanguage\ExpressionLanguage;
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$ast = (new ExpressionLanguage())
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->parse('1 + 2')
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->getNodes()
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;
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// dump the AST nodes for inspection
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var_dump($ast);
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// dump the AST nodes as a string representation
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$astAsString = $ast->dump();
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Manipulating the AST
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--------------------
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The nodes of the AST can also be dumped into a PHP array of nodes to allow
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manipulating them. Call the :method:`Symfony\\Component\\ExpressionLanguage\\ExpressionLanguage::toArray`
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method to turn the AST into an array::
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// ...
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$astAsArray = (new ExpressionLanguage())
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->parse('1 + 2')
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->getNodes()
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->toArray()
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;
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.. _`AST`: https://en.wikipedia.org/wiki/Abstract_syntax_tree

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