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<h1 class="type-name">
<span class="kind">struct</span> Ameba::Rule::Lint::SharedVarInFiber
</h1>
<ul class="superclass-hierarchy"><li class="superclass"><a href="../../../Ameba/Rule/Lint/SharedVarInFiber.html">Ameba::Rule::Lint::SharedVarInFiber</a></li><li class="superclass"><a href="../../../Ameba/Rule/Base.html">Ameba::Rule::Base</a></li><li class="superclass">Struct</li><li class="superclass">Value</li><li class="superclass">Object</li></ul>
<h2>
<a id="overview" class="anchor" href="#overview">
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<use href="#octicon-link"/>
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Overview
</h2>
<p>A rule that disallows using shared variables in fibers,
which are mutated during iterations.</p>
<p>In most cases it leads to unexpected behaviour and is undesired.</p>
<p>For example, having this example:</p>
<pre><code class="language-crystal">n <span class="o">=</span> <span class="n">0</span>
channel <span class="o">=</span> <span class="t">Channel</span>(<span class="t">Int32</span>).<span class="k">new</span>
<span class="k">while</span> n <span class="o">&lt;</span> <span class="n">3</span>
n <span class="o">=</span> n <span class="o">+</span> <span class="n">1</span>
spawn { channel.send n }
<span class="k">end</span>
<span class="n">3</span>.times { puts channel.receive } <span class="c"># =&gt; # 3, 3, 3</span></code></pre>
<p>The problem is there is only one shared between fibers variable <code>n</code>
and when <code>channel.receive</code> is executed its value is <code>3</code>.</p>
<p>To solve this, the code above needs to be rewritten to the following:</p>
<pre><code class="language-crystal">n <span class="o">=</span> <span class="n">0</span>
channel <span class="o">=</span> <span class="t">Channel</span>(<span class="t">Int32</span>).<span class="k">new</span>
<span class="k">while</span> n <span class="o">&lt;</span> <span class="n">3</span>
n <span class="o">=</span> n <span class="o">+</span> <span class="n">1</span>
m <span class="o">=</span> n
spawn <span class="k">do</span> { channel.send m }
<span class="k">end</span>
<span class="n">3</span>.times { puts channel.receive } <span class="c"># =&gt; # 1, 2, 3</span></code></pre>
<p>This rule is able to find the shared variables between fibers, which are mutated
during iterations. So it reports the issue on the first sample and passes on
the second one.</p>
<p>There are also other technics to solve the problem above which are
<a href="https://crystal-lang.org/reference/guides/concurrency.html">officially documented</a></p>
<p>YAML configuration example:</p>
<pre><code class="language-crystal">Lint/SharedVarInFiber:
Enabled: true</code></pre>
<h2>
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Included Modules
</h2>
<ul class="other-types-list">
<li class="other-type">YAML::Serializable</li>
<li class="other-type">YAML::Serializable::Strict</li>
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<h2>
<a id="defined-in" class="anchor" href="#defined-in">
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Defined in:
</h2>
<a href="https://github.com/crystal-ameba/ameba/blob/51b0a07e/src/ameba/rule/lint/shared_var_in_fiber.cr#L53" target="_blank">
ameba/rule/lint/shared_var_in_fiber.cr
</a>
<br/>
<h2>
<a id="constant-summary" class="anchor" href="#constant-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Constant Summary
</h2>
<dl>
<dt class="entry-const" id="MSG">
<strong>MSG</strong> = <code><span class="s">&quot;Shared variable `%s` is used in fiber&quot;</span></code>
</dt>
</dl>
<h2>
<a id="constructors" class="anchor" href="#constructors">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
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Constructors
</h2>
<ul class="list-summary">
<li class="entry-summary">
<a href="#new(ctx:YAML::ParseContext,node:YAML::Nodes::Node)-class-method" class="signature"><strong>.new</strong>(ctx : YAML::ParseContext, node : YAML::Nodes::Node)</a>
</li>
<li class="entry-summary">
<a href="#new(config=nil)-class-method" class="signature"><strong>.new</strong>(config = <span class="n">nil</span>)</a>
<div class="summary"><p>A rule that disallows using shared variables in fibers, which are mutated during iterations.</p></div>
</li>
</ul>
<h2>
<a id="instance-method-summary" class="anchor" href="#instance-method-summary">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
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Instance Method Summary
</h2>
<ul class="list-summary">
<li class="entry-summary">
<a href="#description:String-instance-method" class="signature"><strong>#description</strong> : String</a>
</li>
<li class="entry-summary">
<a href="#description=(description:String)-instance-method" class="signature"><strong>#description=</strong>(description : String)</a>
</li>
<li class="entry-summary">
<a href="#enabled:Bool-instance-method" class="signature"><strong>#enabled</strong> : Bool</a>
</li>
<li class="entry-summary">
<a href="#enabled=(enabled)-instance-method" class="signature"><strong>#enabled=</strong>(enabled)</a>
</li>
<li class="entry-summary">
<a href="#excluded:Array(String)?-instance-method" class="signature"><strong>#excluded</strong> : Array(String)?</a>
</li>
<li class="entry-summary">
<a href="#excluded=(excluded:Array(String)?)-instance-method" class="signature"><strong>#excluded=</strong>(excluded : Array(String)?)</a>
</li>
<li class="entry-summary">
<a href="#severity:Ameba::Severity-instance-method" class="signature"><strong>#severity</strong> : Ameba::Severity</a>
</li>
<li class="entry-summary">
<a href="#severity=(severity)-instance-method" class="signature"><strong>#severity=</strong>(severity)</a>
</li>
<li class="entry-summary">
<a href="#test(source,node,scope:AST::Scope)-instance-method" class="signature"><strong>#test</strong>(source, node, scope : AST::Scope)</a>
</li>
<li class="entry-summary">
<a href="#test(source)-instance-method" class="signature"><strong>#test</strong>(source)</a>
</li>
</ul>
<div class="methods-inherited">
<h3>Instance methods inherited from struct <code><a href="../../../Ameba/Rule/Base.html">Ameba::Rule::Base</a></code></h3>
<a href="../../../Ameba/Rule/Base.html#==(other)-instance-method" class="tooltip">
<span>==(other)</span>
==</a>,
<a href="../../../Ameba/Rule/Base.html#catch(source:Source)-instance-method" class="tooltip">
<span>catch(source : Source)</span>
catch</a>,
<a href="../../../Ameba/Rule/Base.html#excluded?(source)-instance-method" class="tooltip">
<span>excluded?(source)</span>
excluded?</a>,
<a href="../../../Ameba/Rule/Base.html#group-instance-method" class="tooltip">
<span>group</span>
group</a>,
<a href="../../../Ameba/Rule/Base.html#hash-instance-method" class="tooltip">
<span>hash</span>
hash</a>,
<a href="../../../Ameba/Rule/Base.html#name-instance-method" class="tooltip">
<span>name</span>
name</a>,
<a href="../../../Ameba/Rule/Base.html#special?-instance-method" class="tooltip">
<span>special?</span>
special?</a>,
<a href="../../../Ameba/Rule/Base.html#test(source:Source,node:Crystal::ASTNode,*opts)-instance-method" class="tooltip">
<span>test(source : Source, node : Crystal::ASTNode, *opts)<br/>test(source : Source)</span>
test</a>
<h3>Constructor methods inherited from struct <code><a href="../../../Ameba/Rule/Base.html">Ameba::Rule::Base</a></code></h3>
<a href="../../../Ameba/Rule/Base.html#new-class-method" class="tooltip">
<span>new</span>
new</a>
<h3>Class methods inherited from struct <code><a href="../../../Ameba/Rule/Base.html">Ameba::Rule::Base</a></code></h3>
<a href="../../../Ameba/Rule/Base.html#parsed_doc-class-method" class="tooltip">
<span>parsed_doc</span>
parsed_doc</a>
</div>
<h2>
<a id="constructor-detail" class="anchor" href="#constructor-detail">
<svg class="octicon-link" aria-hidden="true">
<use href="#octicon-link"/>
</svg>
</a>
Constructor Detail
</h2>
<div class="entry-detail" id="new(ctx:YAML::ParseContext,node:YAML::Nodes::Node)-class-method">
<div class="signature">
def self.<strong>new</strong>(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
<a class="method-permalink" href="#new(ctx:YAML::ParseContext,node:YAML::Nodes::Node)-class-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="new(config=nil)-class-method">
<div class="signature">
def self.<strong>new</strong>(config = <span class="n">nil</span>)
<a class="method-permalink" href="#new(config=nil)-class-method">#</a>
</div>
<div class="doc">
<p>A rule that disallows using shared variables in fibers,
which are mutated during iterations.</p>
<p>In most cases it leads to unexpected behaviour and is undesired.</p>
<p>For example, having this example:</p>
<pre><code class="language-crystal">n <span class="o">=</span> <span class="n">0</span>
channel <span class="o">=</span> <span class="t">Channel</span>(<span class="t">Int32</span>).<span class="k">new</span>
<span class="k">while</span> n <span class="o">&lt;</span> <span class="n">3</span>
n <span class="o">=</span> n <span class="o">+</span> <span class="n">1</span>
spawn { channel.send n }
<span class="k">end</span>
<span class="n">3</span>.times { puts channel.receive } <span class="c"># =&gt; # 3, 3, 3</span></code></pre>
<p>The problem is there is only one shared between fibers variable <code>n</code>
and when <code>channel.receive</code> is executed its value is <code>3</code>.</p>
<p>To solve this, the code above needs to be rewritten to the following:</p>
<pre><code class="language-crystal">n <span class="o">=</span> <span class="n">0</span>
channel <span class="o">=</span> <span class="t">Channel</span>(<span class="t">Int32</span>).<span class="k">new</span>
<span class="k">while</span> n <span class="o">&lt;</span> <span class="n">3</span>
n <span class="o">=</span> n <span class="o">+</span> <span class="n">1</span>
m <span class="o">=</span> n
spawn <span class="k">do</span> { channel.send m }
<span class="k">end</span>
<span class="n">3</span>.times { puts channel.receive } <span class="c"># =&gt; # 1, 2, 3</span></code></pre>
<p>This rule is able to find the shared variables between fibers, which are mutated
during iterations. So it reports the issue on the first sample and passes on
the second one.</p>
<p>There are also other technics to solve the problem above which are
<a href="https://crystal-lang.org/reference/guides/concurrency.html">officially documented</a></p>
<p>YAML configuration example:</p>
<pre><code class="language-crystal">Lint/SharedVarInFiber:
Enabled: true</code></pre>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-ameba/ameba/blob/51b0a07e/src/ameba/rule/lint/shared_var_in_fiber.cr#L53" target="_blank">View source</a>]
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<h2>
<a id="instance-method-detail" class="anchor" href="#instance-method-detail">
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Instance Method Detail
</h2>
<div class="entry-detail" id="description:String-instance-method">
<div class="signature">
def <strong>description</strong> : String
<a class="method-permalink" href="#description:String-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="description=(description:String)-instance-method">
<div class="signature">
def <strong>description=</strong>(description : String)
<a class="method-permalink" href="#description=(description:String)-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="enabled:Bool-instance-method">
<div class="signature">
def <strong>enabled</strong> : Bool
<a class="method-permalink" href="#enabled:Bool-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="enabled=(enabled)-instance-method">
<div class="signature">
def <strong>enabled=</strong>(enabled)
<a class="method-permalink" href="#enabled=(enabled)-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="excluded:Array(String)?-instance-method">
<div class="signature">
def <strong>excluded</strong> : Array(String)?
<a class="method-permalink" href="#excluded:Array(String)?-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="excluded=(excluded:Array(String)?)-instance-method">
<div class="signature">
def <strong>excluded=</strong>(excluded : Array(String)?)
<a class="method-permalink" href="#excluded=(excluded:Array(String)?)-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="severity:Ameba::Severity-instance-method">
<div class="signature">
def <strong>severity</strong> : <a href="../../../Ameba/Severity.html">Ameba::Severity</a>
<a class="method-permalink" href="#severity:Ameba::Severity-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="severity=(severity)-instance-method">
<div class="signature">
def <strong>severity=</strong>(severity)
<a class="method-permalink" href="#severity=(severity)-instance-method">#</a>
</div>
<br/>
<div>
</div>
</div>
<div class="entry-detail" id="test(source,node,scope:AST::Scope)-instance-method">
<div class="signature">
def <strong>test</strong>(source, node, scope : <a href="../../../Ameba/AST/Scope.html">AST::Scope</a>)
<a class="method-permalink" href="#test(source,node,scope:AST::Scope)-instance-method">#</a>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-ameba/ameba/blob/51b0a07e/src/ameba/rule/lint/shared_var_in_fiber.cr#L64" target="_blank">View source</a>]
</div>
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<div class="entry-detail" id="test(source)-instance-method">
<div class="signature">
def <strong>test</strong>(source)
<a class="method-permalink" href="#test(source)-instance-method">#</a>
</div>
<br/>
<div>
[<a href="https://github.com/crystal-ameba/ameba/blob/51b0a07e/src/ameba/rule/lint/shared_var_in_fiber.cr#L60" target="_blank">View source</a>]
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