short-description: Meson's API to integrate Meson support into an IDE ...

IDE integration

Meson has exporters for Visual Studio and XCode, but writing a custom backend for every IDE out there is not a scalable approach. To solve this problem, Meson provides an API that makes it easy for any IDE or build tools to integrate Meson builds and provide an experience comparable to a solution native to the IDE.

All the resources required for such a IDE integration can be found in the meson-info directory in the build directory.

The first thing to do when setting up a Meson project in an IDE is to select the source and build directories. For this example we assume that the source resides in an Eclipse-like directory called workspace/project and the build tree is nested inside it as workspace/project/build. First, we initialize Meson by running the following command in the source directory.

meson setup builddir

With this command Meson will configure the project and also generate introspection information that is stored in intro-*.json files in the meson-info directory. The introspection dump will be automatically updated when Meson is (re)configured, or the build options change. Thus, an IDE can watch for changes in this directory to know when something changed. Note that meson-info.json guaranteed to be the last file written.

The meson-info directory should contain the following files:

File	Description
`intro-benchmarks.json`	Lists all benchmarks
`intro-buildoptions.json`	Contains a full list of Meson configuration options for the project
`intro-buildsystem_files.json`	Full list of all Meson build files
`intro-dependencies.json`	Lists all dependencies used in the project
`intro-installed.json`	Contains mapping of files to their installed location
`intro-install_plan.json`	Dictionary of data types with the source files and their installation details
`intro-projectinfo.json`	Stores basic information about the project (name, version, etc.)
`intro-targets.json`	Full list of all build targets
`intro-tests.json`	Lists all tests with instructions how to run them

The content of the JSON files is further specified in the remainder of this document.

The `targets` section

The most important file for an IDE is probably intro-targets.json. Here each target with its sources and compiler parameters is specified. The JSON format for one target is defined as follows:

{
    "name": "Name of the target",
    "id": "The internal ID meson uses",
    "type": "<TYPE>",
    "defined_in": "/Path/to/the/targets/meson.build",
    "subproject": null,
    "filename": ["list", "of", "generated", "files"],
    "build_by_default": true / false,
    "target_sources": [],
    "extra_files": ["/path/to/file1.hpp", "/path/to/file2.hpp"],
    "installed": true / false,
}

If the key installed is set to true, the key install_filename will also be present. It stores the installation location for each file in filename. If one file in filename is not installed, its corresponding install location is set to null.

The subproject key specifies the name of the subproject this target was defined in, or null if the target was defined in the top level project.

(New in 0.56.0) The extra_files key lists all files specified via the extra_files kwarg of a build target. See [[executable]].

A target usually generates only one file. However, it is possible for custom targets to have multiple outputs.

Target sources

The intro-targets.json file also stores a list of all source objects of the target in the target_sources. With this information, an IDE can provide code completion for all source files.

{
    "language": "language ID",
    "compiler": ["The", "compiler", "command"],
    "parameters": ["list", "of", "compiler", "parameters"],
    "sources": ["list", "of", "all", "source", "files", "for", "this", "language"],
    "generated_sources": ["list", "of", "all", "source", "files", "that", "where", "generated", "somewhere", "else"]
}

It should be noted that the compiler parameters stored in the parameters differ from the actual parameters used to compile the file. This is because the parameters are optimized for the usage in an IDE to provide autocompletion support, etc. It is thus not recommended to use this introspection information for actual compilation.

Possible values for `type`

The following table shows all valid types for a target.

value of `type`	Description
`executable`	This target will generate an executable file
`static library`	Target for a static library
`shared library`	Target for a shared library
`shared module`	A shared library that is meant to be used with dlopen rather than linking into something else
`custom`	A custom target
`run`	A Meson run target
`jar`	A Java JAR target

Install plan

The intro-install_plan.json file contains a list of the files that are going to be installed on the system.

The data contains a list of files grouped by data type. Each file maps to a dictionary containing the destination and tag keys, with the key being the file location at build time. destination is the destination path using placeholders for the base directories. New keys may be added in the future.

{
    "targets": {
        "/path/to/project/builddir/some_executable": {
            "destination": "{bindir}/some_executable",
            "tag": "runtime"
        },
        "/path/to/project/builddir/libsomelib.so": {
            "destination": "{libdir_shared}/libsomelib.so",
            "tag": "runtime"
        }
    },
    "data": {
        "/path/to/project/some_data": {
            "destination": "{datadir}/some_data",
            "tag": null
        }
    },
    "headers": {
        "/path/to/project/some_header.h": {
            "destination": "{includedir}/some_header.h",
            "tag": "devel"
        }
    }
}

Additionally, the intro-installed.json file contains the mapping of the file path at build time to the absolute system location.

{
    "/path/to/project/builddir/some_executable": "/usr/bin/some_executable",
    "/path/to/project/builddir/libsomelib.so": "/user/lib/libsomelib.so",
    "/path/to/project/some_data": "/usr/share/some_data",
    "/path/to/project/some_header.h": "/usr/include/some_header.h"
}

Using `--targets` without a build directory

It is also possible to get most targets without a build directory. This can be done by running meson introspect --targets /path/to/meson.build.

The generated output is similar to running the introspection with a build directory or reading the intro-targets.json. However, there are some key differences:

The paths in filename now are relative to the future build directory
The install_filename key is completely missing
There is only one entry in target_sources:
- With the language set to unknown
- Empty lists for compiler and parameters and generated_sources
- The sources list should contain all sources of the target

There is no guarantee that the sources list in target_sources is correct. There might be differences, due to internal limitations. It is also not guaranteed that all targets will be listed in the output. It might even be possible that targets are listed, which won't exist when Meson is run normally. This can happen if a target is defined inside an if statement. Use this feature with care.

Build Options

The list of all build options (build type, warning level, etc.) is stored in the intro-buildoptions.json file. Here is the JSON format for each option.

{
    "name": "name of the option",
    "description": "the description",
    "type": "type ID",
    "value": "value depends on type",
    "section": "section ID",
    "machine": "machine ID"
}

The supported types are:

string
boolean
combo
integer
array

For the type combo the key choices is also present. Here all valid values for the option are stored.

The possible values for section are:

core
backend
base
compiler
directory
user
test

The machine key specifies the machine configuration for the option. Possible values are:

any
host
build

To set the options, use the meson configure command.

Since Meson 0.50.0 it is also possible to get the default buildoptions without a build directory by providing the root meson.build instead of a build directory to meson introspect --buildoptions.

Running --buildoptions without a build directory produces the same output as running it with a freshly configured build directory.

However, this behavior is not guaranteed if subprojects are present. Due to internal limitations all subprojects are processed even if they are never used in a real Meson run. Because of this options for the subprojects can differ.

The dependencies section

The list of all found dependencies can be acquired from intro-dependencies.json. Here, the name, version, compiler and linker arguments for a dependency are listed.

Scanning for dependencies with `--scan-dependencies`

It is also possible to get most dependencies used without a build directory. This can be done by running meson introspect --scan-dependencies /path/to/meson.build.

The output format is as follows:

[
  {
    "name": "The name of the dependency",
    "required": true,
    "version": [">=1.2.3"],
    "conditional": false,
    "has_fallback": false
  }
]

The required keyword specifies whether the dependency is marked as required in the meson.build (all dependencies are required by default). The conditional key indicates whether the dependency() function was called inside a conditional block. In a real Meson run these dependencies might not be used, thus they may not be required, even if the required key is set. The has_fallback key just indicates whether a fallback was directly set in the dependency() function. The version key always contains a list of version requirements from the meson.build and not the actual version of the dependency on disc. The version list is empty if no version was specified in the meson.build.

Tests

Compilation and unit tests are done as usual by running the meson compile and meson test commands. A JSON formatted result log can be found in workspace/project/builddir/meson-logs/testlog.json.

When these tests fail, the user probably wants to run the failing test in a debugger. To make this as integrated as possible, extract the tests from the intro-tests.json and intro-benchmarks.json files. This provides you with all the information needed to run the test: what command to execute, command line arguments, environment variable settings and how to process the output.

{
    "name": "name of the test",
    "workdir": "the working directory (can be null)",
    "timeout": "the test timeout",
    "suite": ["list", "of", "test", "suites"],
    "is_parallel": true / false,
    "protocol": "exitcode" / "tap",
    "cmd": ["command", "to", "run"],
    "depends": ["target1-id", "target2-id"],
    "env": {
        "VARIABLE1": "value 1",
        "VARIABLE2": "value 2"
    }
}

The depends entry (since 0.56.0) contains target ids; they can be looked up in the targets introspection data. The executable pointed to by cmd is also included in the entry, as are any arguments to the test that are build products.

Build system files

It is also possible to get Meson build files used in your current project. This can be done by running meson introspect --buildsystem-files /path/to/builddir.

The output format is as follows:

[
    "/Path/to/the/targets/meson.build",
    "/Path/to/the/targets/meson.options",
    "/Path/to/the/targets/subdir/meson.build"
]

Programmatic interface

Meson also provides the meson introspect for project introspection via the command line. Use meson introspect -h to see all available options.

This API can also work without a build directory for the --projectinfo command.

AST of a `meson.build`

Since Meson 0.55.0 it is possible to dump the AST of a meson.build as a JSON object. The interface for this is meson introspect --ast /path/to/meson.build.

Each node of the AST has at least the following entries:

Key	Description
`node`	Type of the node (see following table)
`lineno`	Line number of the node in the file
`colno`	Column number of the node in the file
`end_lineno`	Marks the end of the node (may be the same as `lineno`)
`end_colno`	Marks the end of the node (may be the same as `colno`)

Possible values for node with additional keys:

Node type	Additional keys
`BooleanNode`	`value`: bool
`IdNode`	`value`: str
`NumberNode`	`value`: int
`StringNode`	`value`: str
`ContinueNode`
`BreakNode`
`ArgumentNode`	`positional`: node list; `kwargs`: accept_kwargs
`ArrayNode`	`args`: node
`DictNode`	`args`: node
`EmptyNode`
`OrNode`	`left`: node; `right`: node
`AndNode`	`left`: node; `right`: node
`ComparisonNode`	`left`: node; `right`: node; `ctype`: str
`ArithmeticNode`	`left`: node; `right`: node; `op`: str
`NotNode`	`right`: node
`CodeBlockNode`	`lines`: node list
`IndexNode`	`object`: node; `index`: node
`MethodNode`	`object`: node; `args`: node; `name`: str
`FunctionNode`	`args`: node; `name`: str
`AssignmentNode`	`value`: node; `var_name`: str
`PlusAssignmentNode`	`value`: node; `var_name`: str
`ForeachClauseNode`	`items`: node; `block`: node; `varnames`: list
`IfClauseNode`	`ifs`: node list; `else`: node
`IfNode`	`condition`: node; `block`: node
`UMinusNode`	`right`: node
`TernaryNode`	`condition`: node; `true`: node; `false`: node

We do not guarantee the stability of this format since it is heavily linked to the internal Meson AST. However, breaking changes (removal of a node type or the removal of a key) are unlikely and will be announced in the release notes.

JSON Reference manual

In additional to the online Reference manual, Meson also offers the manual as JSON file. The content of this file is generated from the same source as the online documentation. The two versions are thus identical in content.

This JSON document is attached to every Meson release since 0.60.0. The JSON schema is defined by the class structure given in jsonschema.py

Existing integrations

CLion
Eclipse CDT
Gnome Builder
KDevelop
Meson Syntax Highlighter 3rd party plugin for JetBrains IDEs.
Meson-UI (build GUI for Meson)
mmeson (ccmake clone for Meson)
Qt Creator
vscode-meson extension for VS Code/Codium