Output format: json
The json output format is intended to be used as a machine-readable output, to be interpreted by tooling, although
humans may also use it, as it provides the most detailed output of all supported output formats.
As described on the output-formats page, cargo-msrv reports the status of the program via
events. A processor transforms these events into their output-format. In case of the json output format,
events are almost 1-on-1 serialized to json (there are a few exceptions), and then printed to stderr.
Each json serialized event ends with a newline. Each line thus represents a single serialized event.
To use the json output format, run cargo-msrv with the --output-format json option.
For example, if you want to find the MSRV, you could run cargo msrv --output-format json.
In the next section, you can find a description of the common fields of events. The section thereafter gives an overview of each of the supported events, with for each event its event specific fields.
Events and scope
Cargo MSRV currently reports two types of events: unscoped and scoped events. Unscoped events report about an action on a certain point in time, while scoped events report about an action which took place over a period of time.
In the context of the json output format, an unscoped event will print a single json-line to the stderr, while
a scoped event will print two json-lines to the stderr (one prior to starting the action, and one after the action has
been completed).
Common fields on events
| name | optional | values | description |
|---|---|---|---|
| type | no | Identifies a specific event. | |
| scope | yes | A pair of events which mark the start and end of an action. Together these two individual events are called a scoped event. | |
| scope.id | no | A unique id to match up the two events marking the begin and end of an action. The current incremental nature is an implementation detail and not guaranteed. | |
| scope.marker | no | "start" or "end" | Whether the event marks the beginning or the end of the action |
The type field can be used to identify a specific event.
The scope field is only present for scoped events. The start value (on the marker subfield) marks the start of a scoped event, while end
marks the end of a scoped event.
List of events
Event: Meta
type: meta
description: Reports metadata about the currently running cargo-msrv program instance.
fields:
| name | description |
|---|---|
| instance | Name of the running cargo-msrv program as defined on compile time. This will usually be cargo-msrv. |
| version | Version of the running cargo-msrv program as defined on compile time. |
| sha_short | Short SHA hash of the git commit used to compile and build cargo-msrv. |
| target_triple | Target triple of toolchain used to compile and build cargo-msrv. |
| cargo_features | Features which were enabled during the compilation of cargo-msrv. |
| rustc | Version of rustc used to compile cargo-msrv. |
example:
{"type":"meta","instance":"cargo-msrv","version":"0.15.1","sha_short":"79582b6","target_triple":"x86_64-pc-windows-msvc","cargo_features":"default,rust_releases_dist_source","rustc":"1.62.0"}
Event: FetchIndex
type: fetch_index
description: Prior to determining the MSRV of a crate, we have to figure out which Rust versions are available.
We obtain those using the rust-releases library. The FetchIndex event
reports that the index is being fetched, and details which source is used.
fields:
| name | description |
|---|---|
| source | Place from where the available Rust releases are obtained |
example:
{"type":"fetch_index","source":"rust_changelog","scope":"start"}
{"type":"fetch_index","source":"rust_changelog","scope":"end"}
Event: CheckToolchain
type: check_toolchain
description: The primary way for cargo-msrv to determine whether a given Rust toolchain is compatible with your
crate, is by installing a toolchain and using it to check a crate for compatibility with this toolchain. The
CheckToolchain event is wrapped around this process and notifies you about the start and end of this process.
This event is called as a scoped event, and within it's scope, you'll find the following events: setup_toolchain,
check_method and check_result, which are described in more detail below.
fields:
| name | description |
|---|---|
| toolchain | The toolchain to be located or installed |
| toolchain.version | The Rust version of the toolchain |
| toolchain.target | The target-triple of the toolchain |
example:
{"type":"check_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"start"}
{"type":"check_toolchain","toolchain":{"version":"1.35.0","target":"x86_64-pc-windows-msvc"},"scope":"end"}
Event: SetupToolchain
type: setup_toolchain
description: The primary way for cargo-msrv to determine whether a given Rust toolchain is compatible with your
crate, is by installing a toolchain and using it to check a crate for compatibility with this toolchain. The
SetupToolchain event reports about the process of locating or installing a given toolchain.
fields:
| name | description |
|---|---|
| toolchain | The toolchain to be located or installed |
| toolchain.version | The Rust version of the toolchain |
| toolchain.target | The target-triple of the toolchain |
example:
{"type":"setup_toolchain","toolchain":{"version":"1.47.0","target":"x86_64-pc-windows-msvc"},"scope":"start"}
{"type":"setup_toolchain","toolchain":{"version":"1.47.0","target":"x86_64-pc-windows-msvc"},"scope":"end"}
Event: CheckMethod
type: check_method
description: Reports which method has been used to check whether a toolchain is compatible with a crate.
fields:
| name | optional | condition | description |
|---|---|---|---|
| toolchain | no | The toolchain to be located or installed | |
| toolchain.version | no | The Rust version of the toolchain | |
| toolchain.target | no | The target-triple of the toolchain | |
| method | no | The method used to check for compatibility | |
| method.type | no | The type of method | |
| method.args | no | method.type = rustup_run | The arguments provided to rustup |
| method.path | yes | method.type = rustup_run | The path provided to rustup, if any |
example:
{"type":"check_method","toolchain":{"version":"1.37.0","target":"x86_64-pc-windows-msvc"},"method":{"rustup_run":{"args":["1.37.0-x86_64-pc-windows-msvc","cargo","check"],"path":"..\\air3\\"}}}
Event: CheckResult
type: check_result
description: Reports the result of a cargo-msrv compatibility check.
fields:
| name | optional | condition | description |
|---|---|---|---|
| toolchain | no | The toolchain to be located or installed | |
| toolchain.version | no | The Rust version of the toolchain | |
| toolchain.target | no | The target-triple of the toolchain | |
| is_compatible | no | Boolean value stating compatibility | |
| error | yes | is_compatible = false | Error message of a failed compatibility check, if any |
example:
{"type":"check_result","toolchain":{"version":"1.38.0","target":"x86_64-pc-windows-msvc"},"is_compatible":true}
{"type":"check_result","toolchain":{"version":"1.37.0","target":"x86_64-pc-windows-msvc"},"is_compatible":false,"error":"error: failed to parse lock file at: .\\air3\\Cargo.lock\n\nCaused by:\ninvalid serialized PackageId for key `package.dependencies`\n"}
Event: AuxiliaryOutput
type: auxiliary_output
description: Reports about additional output written by cargo-msrv when applicable. For example, if the
--write-msrv or --write-toolchain-file flag is provided, the MSRV will be written to the Cargo manifest or the
Rust toolchain file respectively. The act of writing this (additional) output is reported by this event.
fields:
| name | optional | condition | description |
|---|---|---|---|
| destination | no | The destination of the auxiliary output | |
| destination.type | no | Type of destination, currently only "file" | |
| destination.path | no | if destination.type = file | Path of the written or amended file |
| item | no | What kind of output is written | |
| item.type | no | Type of output item | |
| item.kind | no | if item.type = msrv | To which field the MSRV was written in the Cargo manifest, "rust-version" or "metadata_fallback" |
| item.kind | no | if item.type = toolchain_file | Which toolchain file kind was written, "legacy" or "toml" |
example:
{"type":"auxiliary_output","destination":{"type":"file","path":"..\\air3\\Cargo.toml"},"item":{"type":"msrv","kind":"rust_version"}}
Event: Progress
type: progress
description: Reports on the progress of an ongoing MSRV search.
fields:
| name | optional | condition | description |
|---|---|---|---|
| current | no | Index of the currently running check into the sorted search space. Starts at 0. | |
| search_space_size | no | The size of the search space. | |
| iteration | no | How many iterations have been completed, plus one for the currently running iteration. Starts at 1. |
Event: SubcommandInit
type: subcommand_init
description: Reports the start of a subcommand flow.
fields:
| name | optional | condition | description |
|---|---|---|---|
| subcommand_id | no | A name identifying the subcommand |
Event: SubcommandResult
type: subcommand_result
description: Reports the outcome of a subcommand flow.
fields:
| name | optional | condition | description |
|---|---|---|---|
| subcommand_id | no | A name identifying the subcommand | |
| result | no | subcommand_id = find | Result of find command |
| result.success | no | subcommand_id = find | Whether the MSRV was found or not |
| result.version | no | subcommand_id = find and result.success = true | The Minimum Supported Rust Version (MSRV) |
| result | no | subcommand_id = list | Result of list command |
| result.variant | no | subcommand_id = list | Type of list output. Either direct-deps or ordered-by-msrv. |
| result.list | no | subcommand_id = list and result.variant = direct-deps | List of direct dependencies of the selected crate |
| result.list.name | no | subcommand_id = list and result.variant = direct-deps | Name of the crate |
| result.list.version | no | subcommand_id = list and result.variant = direct-deps | Version of the crate |
| result.list.msrv | no | subcommand_id = list and result.variant = direct-deps | MSRV of the crate if any, null if the MSRV is not set |
| result.list.dependencies | no | subcommand_id = list and result.variant = direct-deps | Dependencies of the given crate, relevant for the MSRV |
| result.list | no | subcommand_id = list and result.variant = ordered-by-msrv | List of all dependencies relevant for the MSRV, categorised by their MSRV |
| result.list.msrv | no | subcommand_id = list and result.variant = ordered-by-msrv | A value for the MSRV specified by at least one crate |
| result.list.dependencies | no | subcommand_id = list and result.variant = ordered-by-msrv | List of dependencies which specified the same value for the MSRV |
| result | no | subcommand_id = set | Result of set command |
| result.version | no | subcommand_id = set | Which version was set as MSRV |
| result.manifest_path | no | subcommand_id = set | Relative path of file where the MSRV was written to |
| result | no | subcommand_id = show | Result of show command |
| result.version | no | subcommand_id = show | MSRV as set for the given crate |
| result.manifest_path | no | subcommand_id = show | Relative path of file where the MSRV was read from |
| result | no | subcommand_id = verify | Result of verify command |
| result.toolchain | no | subcommand_id = verify | The toolchain to be located or installed |
| result.toolchain.version | no | subcommand_id = verify | The Rust version of the verified toolchain |
| result.toolchain.target | no | subcommand_id = verify | The target-triple of the verified toolchain |
| result.is_compatible | no | subcommand_id = verify | Boolean value stating compatibility |
| result.error | yes | subcommand_id = verify and result.is_compatible = false | Error message of a failed verify check, if any |
example 1: find
{"type":"subcommand_result","subcommand_id":"find","result":{"version":"1.38.0","success":true}}
example 2: list with direct-deps
{"type":"subcommand_result","subcommand_id":"list","result":{"variant":"direct-deps","list":[{"name":"crossbeam-channel","version": "0.5.4","msrv":"1.36.0","dependencies":["cfg-if","crossbeam-utils","num_cpus","rand","signal-hook"]}]}}
Formatted:
{
"type": "subcommand_result",
"subcommand_id": "list",
"result": {
"variant": "direct-deps",
"list": [
{
"name": "crossbeam-channel",
"version": "0.5.4",
"msrv": "1.36.0",
"dependencies": [
"cfg-if",
"crossbeam-utils",
"num_cpus",
"rand",
"signal-hook"
]
}
]
}
}
example 3: list with ordered-by-msrv
{"type":"subcommand_result","subcommand_id":"list","result":{"variant":"ordered-by-msrv","list":[{"msrv":"1.38.0","dependencies":["storyteller"]},{"msrv":"1.36.0","dependencies":["crossbeam-channel","crossbeam-utils"]},{"msrv":null,"dependencies":["cfg-if","lazy_static"]}]}}
Formatted:
{
"type": "subcommand_result",
"subcommand_id": "list",
"result": {
"variant": "ordered-by-msrv",
"list": [
{
"msrv": "1.38.0",
"dependencies": [
"storyteller"
]
},
{
"msrv": "1.36.0",
"dependencies": [
"crossbeam-channel",
"crossbeam-utils"
]
},
{
"msrv": null,
"dependencies": [
"cfg-if",
"lazy_static"
]
}
]
}
}
example 5: set:
{"type":"subcommand_result","subcommand_id":"set","result":{"version":"1.38.0","manifest_path":"..\\air3\\Cargo.toml"}}
example 6: show:
{"type":"subcommand_result","subcommand_id":"show","result":{"version":"1.38.0","manifest_path":"..\\air3\\Cargo.toml"}}
example 7: verify:
{"type":"subcommand_result","subcommand_id":"verify","result":{"toolchain":{"version":"1.38.0","target":"x86_64-pc-windows-msvc"},"is_compatible":true}}
Event: TerminateWithFailure
type: terminate_with_failure
description: Reports about failure which led to program termination with a non-zero exit code.
fields:
| name | optional | description |
|---|---|---|
| reason | no | Reason of failure |
| reason.description | no | Describes why cargo-msrv will terminate with a non-zero exit code |
example:
{"type":"terminate_with_failure","reason":{"description":"MSRV was not specified in Cargo manifest at '..\\air\\Cargo.toml'"}}