Elektra  0.9.5
CODING

intensively (except for file headers).

This document provides an introduction in how the source code of libelektra is organized and how and where to add functionality.

After you downloaded and unpacked Elektra you should see some folders. The most important are:

More about the structure you find in the folder's README.md.

The same guidelines apply to all code in the repository including the plugins.

You are only allowed to break a guideline if there is a good reason to do so. When you do, document the fact as comment next to the code.

Of course, all rules of good software engineering apply: Use meaningful names and keep the software both testable and reusable.

The purpose of the guidelines is to have a consistent style, not to teach programming.

If you see code that breaks guidelines do not hesitate to fix them or at least open issues.

If you see inconsistency within the rules do not hesitate to open an issue about it.

Code is not only for the computer, but it should be readable for humans, too. Up-to-date code comments are essential to make code understandable for others. Thus please use following techniques (in order of preference):

  1. Comment functions with /**/ and Doxygen, see below.
  2. You should also add assertions to state what should be true at a specific position in the code. Their syntax is checked and they are automatically verified at run-time. So they are not only useful for people reading the code but also for tools. Assertions in Elektra are used by:

    #include <kdbassert.h>

    ELEKTRA_ASSERT (condition, "formatted text to be printed when assert fails", ...)

    Note: Do not use assert for user-APIs, always handle arguments of user-APIs like untrusted input.

  3. If the "comment" might be useful to be printed during execution, use logging:

    #include <kdblogger.h>

    ELEKTRA_LOG ("formatted text to be printed according to log filters", ...)

    Read HERE for how to enable the logger.

  4. Otherwise comment within source with // or with /**/ for multi-line comments. Use TODO to indicate that something is not yet done. Before merging, relevant TODOs should be fixed or issues created for left-overs.

The reformat script can ensure most code style rules, but it is obviously not capable of ensuring everything (e.g. naming conventions). So do not give this responsibility out of hands entirely. You can use docker to ensure that you have the correct version of all our reformatting tools at hand.

Example: src/libs/elektra/kdb.c

To guarantee consistent formatting we use clang-format (version 9) to format all C and C++ code in the repository. Since our build servers also check the style for every pull request you might want to make sure you reformat your C/C++ code changes with this tool.

To find out which version of clang-format a certain build server uses please check:

and search for the relevant packages (clang-format, llvm). Currently we use clang-format 9

Installation
macOS

On macOS you can install clang-format using Homebrew either directly:

brew install clang-format

or by installing the whole LLVM infrastructure:

brew install llvm

. Please note, that both of these commands will install current versions of clang-format that might format code a little bit differently than Clang-Format 11 in certain edge cases. If you want you can also install Clang-Format 11 using LLVM 11:

brew install llvm@9
Debian

In Debian the package for Clang-Format 11 is called clang-format-11:

apt-get install clang-format-11

Usage

For the basic use cases you can use clang-format directly. To do that, just call the tool using the option -i and specify the name of the files you want to reformat. For example, if you want to reformat the file src/bindings/cpp/include/kdb.hpp you can use the following command:

# On some systems such as Debian the `clang-format` executable also contains
# the version number. For those systems, please replace `clang-format`,
# with `clang-format-11` in the command below.
clang-format -i src/bindings/cpp/include/kdb.hpp

. While this works fine, if you want to format only a small number of file, formatting multiple files can be quite tedious. For that purpose you can use the script `reformat-c` that reformats all C and C++ code in Elektra’s code base

scripts/dev/reformat-c # This script will probably take some seconds to execute

Tool Integration

If you work on Elektra’s code base regularly you might want to integrate the formatting step directly in your development setup. ClangFormat’s homepage includes a list of integrations for various tools that should help you to do that. Even if this webpage does not list any integrations for your favorite editor or IDE, you can usually add support for external tools such as clang-format to advanced editors or IDEs pretty easily.

TextMate

While TextMate supports clang-format for the current file directly via the keyboard shortcut ctrl++H, the editor does not automatically reformat the file on save. To do that

  1. open the bundle editor (“Bundles” → “Edit Bundles”),
  2. navigate to the “Reformat Code” item of the C bundle (“C” → “Menu Actions” → “Reformat Code”),
  3. insert callback.document.will-save into the field “Semantic Class”, and
  4. change the menu option for the field “Save” to “Nothing”

. After that change TextMate will reformat C and C++ code with clang-format every time you save a file.

Example: src/bindings/cpp/include/kdb.hpp

We use a similar style for CMake as we do for other code:

We use cmake-format to reformat code according to the guidelines given above. Since cmake-format currently does not support tabs, we use the standard command unexpand to fix this issue. For example, to reformat the file CMakeLists.txt in the root folder of the repository we use the following command:

# This command uses `sponge`, which is part of the [moreutils](https://joeyh.name/code/moreutils/) package.
cmake-format CMakeLists.txt | unexpand | sponge CMakeLists.txt

Installation

Since cmake-format is written in Python you usually install it via Python’s package manager pip:

# Install cmake format `0.6.3` with support for YAML config files
pip install cmake-format[yaml]==0.6.3

. Please make sure, that you install the correct version (0.6.3) of cmake format:

cmake-format --version
#> 0.6.3

, since otherwise the formatted code might look quite different.

We also use the moreutils in our CMake formatting script, which you can install on macOS using Homebrew:

brew install moreutils

and on Debian using apt-get:

apt-get install moreutils

Usage

If you want to reformat the whole codebase you can use the script `reformat-cmake`:

scripts/dev/reformat-cmake # Running this script for the whole code base takes some time.

. To reformat specific files add a list of file paths after the command:

# The command below reformats the file `cmake/CMakeLists.txt`.
scripts/dev/reformat-cmake cmake/CMakeLists.txt

Tool Integration

If you work on CMake code quite often you probably want to integrate cmake format into your development workflow. The homepage of cmake format list some integration options.

TextMate

While TextMate does not support cmake format directly, you can quickly create a command that applies cmake-format every time you save a CMake file yourself. The steps below show one option to do that.

  1. Open the “Bundle Editor”: Press ^ + + + B
  2. Create a new command:
    1. Press + N
    2. Select “Command”
    3. Press the button “Create”
  3. Configure your new command
    1. Use “Reformat Document” or a similar text as “Name”
    2. Enter source.cmake in the field “Scope Selector”
    3. Use ^ + + H as “Key Equivalent”
    4. Copy the text callback.document.will-save into the field “Semantic Class”
    5. Select “Document” as “Input”
    6. Select “Replace Document” in the dropdown menu for the option “Output”
    7. Select “Line Interpolation” in the menu “Caret Placement”
    8. Copy the following code into the text field:

      ``` #!/bin/bash

      set -o pipefail if ! "${TM_CMAKE_FORMAT:-cmake-format}" - | ${TM_CMAKE_FORMAT_FILTER:-tee}; then . "$TM_SUPPORT_PATH/lib/bash_init.sh" exit_show_tool_tip fi ```

    9. Save your new command: + S
    10. Store the value unexpand in the variable TM_CMAKE_FORMAT_FILTER. To do that save the text
TM_CMAKE_FORMAT_FILTER = "unexpand"

in a file called .tm_properties in the root of Elektra’s repository.

Please follow Google Java Style Guide for Groovy (used by Jenkins) files.

Most notably use:

We use a similar style for Java and C/C++ code. This means we also use clang-format to format Java code. For more information on how to install clang-format, please take a look at the subheading “Clang Format” of the “C Guidelines”.

Usage

If you want to reformat all Java files in the repository you can use the script `reformat-java`:

scripts/dev/reformat-java

. To reformat specific files add a list of file paths after the command:

# The command below reformats the file `cmake/CMakeLists.txt`.
scripts/dev/reformat-java src/bindings/jna/libelektra/src/main/java/org/libelektra/KDB.java
TextMate

The steps below show you how to create a TextMate command that formats a documents with [clang-format][] every time you save it.

  1. Open the “Bundle Editor”: Press ^ + + + B
  2. Create a new command:
    1. Press + N
    2. Select “Command”
    3. Press the button “Create”
  3. Configure your new command
    1. Use “Reformat Document” or a similar text as “Name”
    2. Enter source.java in the field “Scope Selector”
    3. Use ^ + + H as “Key Equivalent”
    4. Copy the text callback.document.will-save into the field “Semantic Class”
    5. Select “Document” as “Input”
    6. Select “Replace Input” in the dropdown menu for the option “Output”
    7. Select “Line Interpolation” in the menu “Caret Placement”
    8. Copy the following code into the text field:

      ``` #!/bin/bash

      if ! "${TM_CLANG_FORMAT:-clang-format}" \ -style="${TM_CLANG_FORMAT_STYLE:-file}" \ -assume-filename="${TM_FILEPATH}"; then . "$TM_SUPPORT_PATH/lib/bash_init.sh" exit_show_tool_tip fi ```

    9. Save your new command: + S

We use prettier to format JavaScript files.

Installation
macOS

On macOS you can install prettier using Homebrew:

brew install prettier
General

To install prettier using Node’s package manager npm you can use the command below

npm install --global prettier@1.19.1

Usage

To format all JavaScript files in the repository you can use the script `reformat-javascript`:

scripts/dev/reformat-javascript

. To format only some files, please specify a list of filenames after the command:

scripts/dev/reformat-markdown src/tools/qt-gui/qml/ErrorDialogCreator.js # Reformat this file

We use prettier to format the documentation according to the guidelines given above.

Under certain exceptional circumstances you might want to prevent prettier from formatting certain parts of a Markdown file. To do that you can

Installation

For information on how to install the tool, please take a look at “JavaScript Guidelines” → “Prettier” → “Installation”.

Usage

You can format all Markdown files in the repository using the script `reformat-markdown`:

scripts/dev/reformat-markdown

. To format only some files, please specify a list of filenames after the command:

scripts/dev/reformat-markdown doc/CODING.md # Reformat this file

Tool Integration

The homepage of Prettier lists various options to integrate the tool into your workflow.

TextMate

To reformat a Markdown document in TextMate every time you save it, please follow the steps listed below.

  1. Open the “Bundle Editor”: Press ^ + + + B
  2. Create a new command:
    1. Press + N
    2. Select “Command”
    3. Press the button “Create”
  3. Configure your new command
    1. Use “Reformat Document” or a similar text as “Name”
    2. Enter text.html.markdown in the field “Scope Selector”
    3. Use ^ + + H as “Key Equivalent”
    4. Copy the text callback.document.will-save into the field “Semantic Class”
    5. Select “Document” as “Input”
    6. Select “Replace Input” in the dropdown menu for the option “Output”
    7. Select “Line Interpolation” in the menu “Caret Placement”
    8. Copy the following code into the text field:

      ``` #!/bin/bash

      if ! "${TM_PRETTIER:-prettier}" –stdin –stdin-filepath "${TM_FILEPATH}" then . "$TM_SUPPORT_PATH/lib/bash_init.sh" exit_show_tool_tip fi ```

    9. Save your new command: + S

We use shfmt to format Shell files in the repository.

Installation
macOS

You can install shfmt on macOS using Homebrew:

brew install shfmt
General

shfmt’s GitHub release page offers binaries for various operating systems. For example, to install the binary for the current user on Linux you can use the following command:

mkdir -p "$HOME/bin" && cd "$HOME/bin" && \
curl -L "https://github.com/mvdan/sh/releases/download/v2.6.4/shfmt_v2.6.4_linux_amd64" -o shfmt && \
chmod u+x shfmt

. Please note that you have to make sure, that your PATH includes $HOME/bin, if you use the command above:

export PATH=$PATH:"$HOME/bin"

Usage

We provide the script `reformat-shell` that formats the whole codebase with shfmt:

scripts/dev/reformat-shell

. You can also reformat specific files by listing filenames after the script:

`` scripts/dev/reformat-shell scripts/dev/reformat-shell # Reformat the source ofreformat-shell`

.
##### Tool Integration
The GitHub project page of [`shfmt`][] offers some options to integrate the tool into your development workflow [here](https://github.com/mvdan/sh#related-projects).
###### TextMate
The steps below show you how to create a [TextMate][] command that formats a documents with [`shfmt`][] every time you save it.
1. Open the “Bundle Editor”: Press <kbd>^</kbd> + <kbd>⌥</kbd> + <kbd>⌘</kbd> + <kbd>B</kbd>
2. Create a new command:
1. Press <kbd>⌘</kbd> + <kbd>N</kbd>
2. Select “Command”
3. Press the button “Create”
3. Configure your new command
1. Use “Reformat Document” or a similar text as “Name”
2. Enter `source.shell` in the field “Scope Selector”
3. Use <kbd>^</kbd> + <kbd>⇧</kbd> + <kbd>H</kbd> as “Key Equivalent”
4. Copy the text `callback.document.will-save` into the field “Semantic Class”
5. Select “Document” as “Input”
6. Select “Replace Input” in the dropdown menu for the option “Output”
7. Select “Line Interpolation” in the menu “Caret Placement”
8. Copy the following code into the text field:

#!/bin/bash

if ! "${TM_SHFMT_FORMAT:-shfmt}" -s -sr; then . "$TM_SUPPORT_PATH/lib/bash_init.sh" exit_show_tool_tip fi ```

  1. Save your new command: + S

doxygen is used to document the API and to build the html and pdf output. We also support the import of Markdown pages. Doxygen 1.8.8 or later is required for this feature (Anyways you can find the API Doc online). Links between Markdown files will be converted with the Markdown Link Converter. Markdown pages are used in the pdf, therefore watch which characters you use and provide a proper encoding!

Files should start with:

```c /**