Merge pull request #43423 from Calinou/doc-assert-avoid-side-effects

Clarify that code in `assert()` should avoid side effects
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Rémi Verschelde 2020-11-10 11:31:28 +01:00 committed by GitHub
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@ -94,14 +94,15 @@
<argument index="1" name="message" type="String" default="&quot;&quot;">
</argument>
<description>
Asserts that the [code]condition[/code] is [code]true[/code]. If the [code]condition[/code] is [code]false[/code], an error is generated and the program is halted until you resume it. Only executes in debug builds, or when running the game from the editor. Use it for debugging purposes, to make sure a statement is [code]true[/code] during development.
Asserts that the [code]condition[/code] is [code]true[/code]. If the [code]condition[/code] is [code]false[/code], an error is generated. When running from the editor, the running project will also be paused until you resume it. This can be used as a stronger form of [method push_error] for reporting errors to project developers or add-on users.
[b]Note:[/b] For performance reasons, the code inside [method assert] is only executed in debug builds or when running the project from the editor. Don't include code that has side effects in an [method assert] call. Otherwise, the project will behave differently when exported in release mode.
The optional [code]message[/code] argument, if given, is shown in addition to the generic "Assertion failed" message. You can use this to provide additional details about why the assertion failed.
[codeblock]
# Imagine we always want speed to be between 0 and 20
speed = -10
# Imagine we always want speed to be between 0 and 20.
var speed = -10
assert(speed &lt; 20) # True, the program will continue
assert(speed &gt;= 0) # False, the program will stop
assert(speed &gt;= 0 &amp;&amp; speed &lt; 20) # You can also combine the two conditional statements in one check
assert(speed &gt;= 0 and speed &lt; 20) # You can also combine the two conditional statements in one check
assert(speed &lt; 20, "speed = %f, but the speed limit is 20" % speed) # Show a message with clarifying details
[/codeblock]
</description>