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Rust: Port the code examples to Rust / CodeQL for Rust.

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Geoffrey White
2025-09-23 11:55:33 +01:00
parent 1211dc8f3c
commit db3d177300
1 changed files with 31 additions and 30 deletions
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47
docs/codeql/codeql-language-guides/basic-query-for-rust-code.rst
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@@ -31,16 +31,16 @@ Running a quick query
import rust
from IfStmt ifStmt
where ifStmt.getThen().(BraceStmt).getNumberOfElements() = 0
select ifStmt, "This 'if' statement is redundant."
from IfExpr ifExpr
where ifExpr.getThen().(BlockExpr).getStmtList().getNumberOfStmtOrExpr() = 0
select ifExpr, "This 'if' statement is redundant."
.. include:: ../reusables/vs-code-basic-instructions/run-quick-query-2.rst
.. image:: ../images/codeql-for-visual-studio-code/basic-rust-query-results-1.png
:align: center
If any matching code is found, click a link in the ``ifStmt`` column to open the file and highlight the matching ``if`` statement.
If any matching code is found, click a link in the ``ifExpr`` column to open the file and highlight the matching ``if`` expression.
.. image:: ../images/codeql-for-visual-studio-code/basic-rust-query-results-2.png
:align: center
@@ -52,24 +52,25 @@ About the query structure
After the initial ``import`` statement, this simple query comprises three parts that serve similar purposes to the FROM, WHERE, and SELECT parts of an SQL query.
+------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------+
+----------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------+
| Query part | Purpose | Details |
+==================================================================+===================================================================================================================+=================================================================================================+
+==================================================================================+===================================================================================================================+======================================================================================================+
| ``import rust`` | Imports the standard CodeQL AST libraries for Rust. | Every query begins with one or more ``import`` statements. |
+------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------+
| ``from IfStmt ifStmt`` | Defines the variables for the query. | We use: an ``IfStmt`` variable for ``if`` statements. |
+----------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------+
| ``from IfExpr ifExpr`` | Defines the variables for the query. | We use: an ``IfExpr`` variable for ``if`` expressions. |
| | Declarations are of the form: | |
| | ``<type> <variable name>`` | |
+------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------+
| ``where ifStmt.getThen().(BraceStmt).getNumberOfElements() = 0`` | Defines a condition on the variables. | ``ifStmt.getThen()``: gets the ``then`` branch of the ``if`` expression. |
| | | ``.(BraceStmt)``: requires that the ``then`` branch is a brace statement (``{ }``). |
| | | ``.getNumberOfElements() = 0``: requires that the brace statement contains no child statements. |
+------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------+
| ``select ifStmt, "This 'if' statement is redundant."`` | Defines what to report for each match. | Reports the resulting ``if`` statement with a string that explains the problem. |
+----------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------+
| ``where ifExpr.getThen().(BlockExpr).getStmtList().getNumberOfStmtOrExpr() = 0`` | Defines a condition on the variables. | ``ifExpr.getThen()``: gets the ``then`` branch of the ``if`` expression. |
| | | ``.(BlockExpr)``: requires that the ``then`` branch is a block expression (``{ }``). |
| | | ``.getStmtList()``: gets the list of things in the block. |
| | | ``.getNumberOfStmtOrExpr() = 0``: requires that there are no statements or expressions in the block. |
+----------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------+
| ``select ifExpr, "This 'if' expression is redundant."`` | Defines what to report for each match. | Reports the resulting ``if`` expression with a string that explains the problem. |
| | | |
| | ``select`` statements for queries that are used to find instances of poor coding practice are always in the form: | |
| | ``select <program element>, "<alert message>"`` | |
+------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------+
+----------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------+
Extend the query
----------------
@@ -79,7 +80,7 @@ Query writing is an inherently iterative process. You write a simple query and t
Remove false positive results
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Browsing the results of our basic query shows that it could be improved. Among the results you are likely to find examples of ``if`` statements with an ``else`` branch, where an empty ``then`` branch does serve a purpose. For example:
Browsing the results of our basic query shows that it could be improved. Among the results you are likely to find examples of ``if`` expressions with an ``else`` branch, where an empty ``then`` branch does serve a purpose. For example:
.. code-block:: rust
@@ -89,23 +90,23 @@ Browsing the results of our basic query shows that it could be improved. Among t
handleError("unrecognized option")
}
In this case, identifying the ``if`` statement with the empty ``then`` branch as redundant is a false positive. One solution to this is to modify the query to select ``if`` statements where both the ``then`` and ``else`` branches are missing.
In this case, identifying the ``if`` expression with the empty ``then`` branch as redundant is a false positive. One solution to this is to modify the query to select ``if`` expressions where both the ``then`` and ``else`` branches are missing.
To exclude ``if`` statements that have an ``else`` branch:
To exclude ``if`` expressions that have an ``else`` branch:
#. Add the following to the where clause:
.. code-block:: ql
and not exists(ifStmt.getElse())
and not exists(ifExpr.getElse())
The ``where`` clause is now:
.. code-block:: ql
where
ifStmt.getThen().(BraceStmt).getNumberOfElements() = 0 and
not exists(ifStmt.getElse())
ifExpr.getThen().(BlockExpr).getStmtList().getNumberOfStmtOrExpr() = 0 and
not exists(ifExpr.getElse())
#. Re-run the query.
@@ -123,8 +124,8 @@ Further reading
.. |language-code| replace:: ``rust``
.. |example-url| replace:: https://github.com/alamofire/alamofire
.. |example-url| replace:: https://github.com/rust-lang/rustlings
.. |image-quick-query| image:: ../images/codeql-for-visual-studio-code/quick-query-tab-rust.png
.. |result-col-1| replace:: The first column corresponds to the expression ``ifStmt`` and is linked to the location in the source code of the project where ``ifStmt`` occurs.
.. |result-col-1| replace:: The first column corresponds to the expression ``ifExpr`` and is linked to the location in the source code of the project where ``ifExpr`` occurs.