The Meson Build System
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365 lines
15 KiB
365 lines
15 KiB
--- |
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short-description: Meson's API to integrate Meson support into an IDE |
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... |
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# IDE integration |
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Meson has exporters for Visual Studio and XCode, but writing a custom |
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backend for every IDE out there is not a scalable approach. To solve |
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this problem, Meson provides an API that makes it easy for any IDE or |
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build tools to integrate Meson builds and provide an experience |
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comparable to a solution native to the IDE. |
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All the resources required for such a IDE integration can be found in |
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the `meson-info` directory in the build directory. |
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The first thing to do when setting up a Meson project in an IDE is to |
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select the source and build directories. For this example we assume |
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that the source resides in an Eclipse-like directory called |
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`workspace/project` and the build tree is nested inside it as |
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`workspace/project/build`. First, we initialize Meson by running the |
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following command in the source directory. |
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meson builddir |
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With this command Meson will configure the project and also generate |
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introspection information that is stored in `intro-*.json` files in |
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the `meson-info` directory. The introspection dump will be |
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automatically updated when Meson is (re)configured, or the build |
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options change. Thus, an IDE can watch for changes in this directory |
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to know when something changed. Note that `meson-info.json` guaranteed |
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to be the last file written. |
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The `meson-info` directory should contain the following files: |
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| File | Description | |
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| ------------------------------ | ------------------------------------------------------------------- | |
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| `intro-benchmarks.json` | Lists all benchmarks | |
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| `intro-buildoptions.json` | Contains a full list of Meson configuration options for the project | |
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| `intro-buildsystem_files.json` | Full list of all Meson build files | |
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| `intro-dependencies.json` | Lists all dependencies used in the project | |
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| `intro-installed.json` | Contains mapping of files to their installed location | |
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| `intro-projectinfo.json` | Stores basic information about the project (name, version, etc.) | |
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| `intro-targets.json` | Full list of all build targets | |
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| `intro-tests.json` | Lists all tests with instructions how to run them | |
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The content of the JSON files is further specified in the remainder of |
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this document. |
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## The `targets` section |
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The most important file for an IDE is probably `intro-targets.json`. |
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Here each target with its sources and compiler parameters is |
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specified. The JSON format for one target is defined as follows: |
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```json |
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{ |
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"name": "Name of the target", |
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"id": "The internal ID meson uses", |
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"type": "<TYPE>", |
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"defined_in": "/Path/to/the/targets/meson.build", |
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"subproject": null, |
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"filename": ["list", "of", "generated", "files"], |
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"build_by_default": true / false, |
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"target_sources": [], |
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"extra_files": ["/path/to/file1.hpp", "/path/to/file2.hpp"], |
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"installed": true / false, |
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} |
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``` |
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If the key `installed` is set to `true`, the key `install_filename` |
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will also be present. It stores the installation location for each |
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file in `filename`. If one file in `filename` is not installed, its |
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corresponding install location is set to `null`. |
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The `subproject` key specifies the name of the subproject this target |
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was defined in, or `null` if the target was defined in the top level |
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project. |
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*(New in 0.56.0)* The `extra_files` key lists all files specified via |
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the `extra_files` kwarg of a build target. See |
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[`executable()`](Reference-manual.md#executable). |
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A target usually generates only one file. However, it is possible for |
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custom targets to have multiple outputs. |
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### Target sources |
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The `intro-targets.json` file also stores a list of all source objects |
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of the target in the `target_sources`. With this information, an IDE |
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can provide code completion for all source files. |
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```json |
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{ |
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"language": "language ID", |
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"compiler": ["The", "compiler", "command"], |
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"parameters": ["list", "of", "compiler", "parameters"], |
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"sources": ["list", "of", "all", "source", "files", "for", "this", "language"], |
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"generated_sources": ["list", "of", "all", "source", "files", "that", "where", "generated", "somewhere", "else"] |
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} |
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``` |
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It should be noted that the compiler parameters stored in the |
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`parameters` differ from the actual parameters used to compile the |
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file. This is because the parameters are optimized for the usage in an |
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IDE to provide autocompletion support, etc. It is thus not recommended |
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to use this introspection information for actual compilation. |
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### Possible values for `type` |
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The following table shows all valid types for a target. |
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| value of `type` | Description | |
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| ---------------- | --------------------------------------------------------------------------------------------- | |
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| `executable` | This target will generate an executable file | |
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| `static library` | Target for a static library | |
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| `shared library` | Target for a shared library | |
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| `shared module` | A shared library that is meant to be used with dlopen rather than linking into something else | |
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| `custom` | A custom target | |
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| `run` | A Meson run target | |
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| `jar` | A Java JAR target | |
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### Using `--targets` without a build directory |
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It is also possible to get most targets without a build directory. |
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This can be done by running `meson introspect --targets |
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/path/to/meson.build`. |
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The generated output is similar to running the introspection with a |
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build directory or reading the `intro-targets.json`. However, there |
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are some key differences: |
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- The paths in `filename` now are _relative_ to the future build directory |
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- The `install_filename` key is completely missing |
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- There is only one entry in `target_sources`: |
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- With the language set to `unknown` |
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- Empty lists for `compiler` and `parameters` and `generated_sources` |
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- The `sources` list _should_ contain all sources of the target |
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There is no guarantee that the sources list in `target_sources` is |
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correct. There might be differences, due to internal limitations. It |
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is also not guaranteed that all targets will be listed in the output. |
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It might even be possible that targets are listed, which won't exist |
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when Meson is run normally. This can happen if a target is defined |
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inside an if statement. Use this feature with care. |
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## Build Options |
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The list of all build options (build type, warning level, etc.) is |
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stored in the `intro-buildoptions.json` file. Here is the JSON format |
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for each option. |
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```json |
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{ |
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"name": "name of the option", |
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"description": "the description", |
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"type": "type ID", |
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"value": "value depends on type", |
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"section": "section ID", |
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"machine": "machine ID" |
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} |
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``` |
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The supported types are: |
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- string |
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- boolean |
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- combo |
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- integer |
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- array |
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For the type `combo` the key `choices` is also present. Here all valid |
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values for the option are stored. |
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The possible values for `section` are: |
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- core |
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- backend |
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- base |
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- compiler |
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- directory |
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- user |
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- test |
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The `machine` key specifies the machine configuration for the option. |
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Possible values are: |
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- any |
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- host |
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- build |
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To set the options, use the `meson configure` command. |
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Since Meson 0.50.0 it is also possible to get the default buildoptions |
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without a build directory by providing the root `meson.build` instead |
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of a build directory to `meson introspect --buildoptions`. |
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Running `--buildoptions` without a build directory produces the same |
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output as running it with a freshly configured build directory. |
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However, this behavior is not guaranteed if subprojects are present. |
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Due to internal limitations all subprojects are processed even if they |
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are never used in a real Meson run. Because of this options for the |
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subprojects can differ. |
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## The dependencies section |
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The list of all _found_ dependencies can be acquired from |
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`intro-dependencies.json`. Here, the name, version, compiler and |
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linker arguments for a dependency are listed. |
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### Scanning for dependecie with `--scan-dependencies` |
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It is also possible to get most dependencies used without a build |
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directory. This can be done by running `meson introspect |
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--scan-dependencies /path/to/meson.build`. |
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The output format is as follows: |
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```json |
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[ |
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{ |
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"name": "The name of the dependency", |
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"required": true, |
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"version": [">=1.2.3"], |
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"conditional": false, |
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"has_fallback": false |
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} |
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] |
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``` |
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The `required` keyword specifies whether the dependency is marked as |
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required in the `meson.build` (all dependencies are required by |
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default). The `conditional` key indicates whether the `dependency()` |
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function was called inside a conditional block. In a real Meson run |
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these dependencies might not be used, thus they _may_ not be required, |
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even if the `required` key is set. The `has_fallback` key just |
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indicates whether a fallback was directly set in the `dependency()` |
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function. The `version` key always contains a list of version |
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requirements from the `meson.build` and **not** the actual version of |
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the dependency on disc. The version list is empty if no version was |
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specified in the `meson.build`. |
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## Tests |
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Compilation and unit tests are done as usual by running the `meson |
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compile` and `meson test` commands. A JSON formatted result log can be |
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found in `workspace/project/builddir/meson-logs/testlog.json`. |
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When these tests fail, the user probably wants to run the failing test |
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in a debugger. To make this as integrated as possible, extract the |
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tests from the `intro-tests.json` and `intro-benchmarks.json` files. |
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This provides you with all the information needed to run the test: |
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what command to execute, command line arguments, environment variable |
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settings and how to process the output. |
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```json |
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{ |
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"name": "name of the test", |
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"workdir": "the working directory (can be null)", |
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"timeout": "the test timeout", |
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"suite": ["list", "of", "test", "suites"], |
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"is_parallel": true / false, |
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"protocol": "exitcode" / "tap", |
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"cmd": ["command", "to", "run"], |
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"depends": ["target1-id", "target2-id"], |
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"env": { |
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"VARIABLE1": "value 1", |
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"VARIABLE2": "value 2" |
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} |
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} |
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``` |
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The `depends` entry *(since 0.56.0)* contains target ids; they can be |
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looked up in the targets introspection data. The executable pointed to |
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by `cmd` is also included in the entry, as are any arguments to the |
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test that are build products. |
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## Build system files |
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It is also possible to get Meson build files used in your current |
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project. This can be done by running `meson introspect |
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--buildsystem-files /path/to/builddir`. |
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The output format is as follows: |
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```json |
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[ |
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"/Path/to/the/targets/meson.build", |
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"/Path/to/the/targets/meson_options.txt", |
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"/Path/to/the/targets/subdir/meson.build" |
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] |
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``` |
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# Programmatic interface |
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Meson also provides the `meson introspect` for project introspection |
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via the command line. Use `meson introspect -h` to see all available |
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options. |
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This API can also work without a build directory for the |
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`--projectinfo` command. |
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# AST of a `meson.build` |
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Since Meson *0.55.0* it is possible to dump the AST of a `meson.build` |
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as a JSON object. The interface for this is `meson introspect --ast |
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/path/to/meson.build`. |
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Each node of the AST has at least the following entries: |
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| Key | Description | |
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| ------------ | ------------------------------------------------------- | |
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| `node` | Type of the node (see following table) | |
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| `lineno` | Line number of the node in the file | |
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| `colno` | Column number of the node in the file | |
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| `end_lineno` | Marks the end of the node (may be the same as `lineno`) | |
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| `end_colno` | Marks the end of the node (may be the same as `colno`) | |
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Possible values for `node` with additional keys: |
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| Node type | Additional keys | |
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| -------------------- | ------------------------------------------------ | |
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| `BooleanNode` | `value`: bool | |
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| `IdNode` | `value`: str | |
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| `NumberNode` | `value`: int | |
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| `StringNode` | `value`: str | |
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| `ContinueNode` | | |
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| `BreakNode` | | |
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| `ArgumentNode` | `positional`: node list; `kwargs`: accept_kwargs | |
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| `ArrayNode` | `args`: node | |
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| `DictNode` | `args`: node | |
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| `EmptyNode` | | |
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| `OrNode` | `left`: node; `right`: node | |
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| `AndNode` | `left`: node; `right`: node | |
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| `ComparisonNode` | `left`: node; `right`: node; `ctype`: str | |
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| `ArithmeticNode` | `left`: node; `right`: node; `op`: str | |
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| `NotNode` | `right`: node | |
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| `CodeBlockNode` | `lines`: node list | |
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| `IndexNode` | `object`: node; `index`: node | |
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| `MethodNode` | `object`: node; `args`: node; `name`: str | |
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| `FunctionNode` | `args`: node; `name`: str | |
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| `AssignmentNode` | `value`: node; `var_name`: str | |
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| `PlusAssignmentNode` | `value`: node; `var_name`: str | |
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| `ForeachClauseNode` | `items`: node; `block`: node; `varnames`: list | |
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| `IfClauseNode` | `ifs`: node list; `else`: node | |
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| `IfNode` | `condition`: node; `block`: node | |
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| `UMinusNode` | `right`: node | |
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| `TernaryNode` | `condition`: node; `true`: node; `false`: node | |
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We do not guarantee the stability of this format since it is heavily |
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linked to the internal Meson AST. However, breaking changes (removal |
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of a node type or the removal of a key) are unlikely and will be |
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announced in the release notes. |
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# Existing integrations |
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- [Gnome Builder](https://wiki.gnome.org/Apps/Builder) |
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- [KDevelop](https://www.kdevelop.org) |
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- [Eclipse CDT](https://www.eclipse.org/cdt/) (experimental) |
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- [Meson Cmake Wrapper](https://github.com/prozum/meson-cmake-wrapper) (for cmake IDEs) (currently unmaintained !!) |
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- [Meson-UI](https://github.com/michaelbadcrumble/meson-ui) (Meson build GUI) |
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- [Meson Syntax Highlighter](https://plugins.jetbrains.com/plugin/13269-meson-syntax-highlighter) plugin for JetBrains IDEs. |
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- [asabil.meson](https://open-vsx.org/extension/asabil/meson) extension for VS Code/Codium |
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- [Qt Creator](https://doc.qt.io/qtcreator/creator-project-meson.html)
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