-
Notifications
You must be signed in to change notification settings - Fork 12.7k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Auto merge of #64925 - ehuss:document-json, r=Mark-Simulacrum
Document JSON message output. This documents the JSON messages in the rustc book.
- Loading branch information
Showing
3 changed files
with
240 additions
and
1 deletion.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,231 @@ | ||
| # JSON Output | ||
|
|
||
| This chapter documents the JSON structures emitted by `rustc`. JSON may be | ||
| enabled with the [`--error-format=json` flag][option-error-format]. Additional | ||
| options may be specified with the [`--json` flag][option-json] which can | ||
| change which messages are generated, and the format of the messages. | ||
|
|
||
| JSON messages are emitted one per line to stderr. | ||
|
|
||
| If parsing the output with Rust, the | ||
| [`cargo_metadata`](https://crates.io/crates/cargo_metadata) crate provides | ||
| some support for parsing the messages. | ||
|
|
||
| When parsing, care should be taken to be forwards-compatible with future changes | ||
| to the format. Optional values may be `null`. New fields may be added. Enumerated | ||
| fields like "level" or "suggestion_applicability" may add new values. | ||
|
|
||
| ## Diagnostics | ||
|
|
||
| Diagnostic messages provide errors or possible concerns generated during | ||
| compilation. `rustc` provides detailed information about where the diagnostic | ||
| originates, along with hints and suggestions. | ||
|
|
||
| Diagnostics are arranged in a parent/child relationship where the parent | ||
| diagnostic value is the core of the diagnostic, and the attached children | ||
| provide additional context, help, and information. | ||
|
|
||
| Diagnostics have the following format: | ||
|
|
||
| ```javascript | ||
| { | ||
| /* The primary message. */ | ||
| "message": "unused variable: `x`", | ||
| /* The diagnostic code. | ||
| Some messages may set this value to null. | ||
| */ | ||
| "code": { | ||
| /* A unique string identifying which diagnostic triggered. */ | ||
| "code": "unused_variables", | ||
| /* An optional string explaining more detail about the diagnostic code. */ | ||
| "explanation": null | ||
| }, | ||
| /* The severity of the diagnostic. | ||
| Values may be: | ||
| - "error": A fatal error that prevents compilation. | ||
| - "warning": A possible error or concern. | ||
| - "note": Additional information or context about the diagnostic. | ||
| - "help": A suggestion on how to resolve the diagnostic. | ||
| - "failure-note": A note attached to the message for further information. | ||
| - "error: internal compiler error": Indicates a bug within the compiler. | ||
| */ | ||
| "level": "warning", | ||
| /* An array of source code locations to point out specific details about | ||
| where the diagnostic originates from. This may be empty, for example | ||
| for some global messages, or child messages attached to a parent. | ||
| Character offsets are offsets of Unicode Scalar Values. | ||
| */ | ||
| "spans": [ | ||
| { | ||
| /* The file where the span is located. | ||
| For spans located within a macro expansion, this will be the | ||
| name of the expanded macro in the format "<MACRONAME macros>". | ||
| */ | ||
| "file_name": "lib.rs", | ||
| /* The byte offset where the span starts (0-based, inclusive). */ | ||
| "byte_start": 21, | ||
| /* The byte offset where the span ends (0-based, exclusive). */ | ||
| "byte_end": 22, | ||
| /* The first line number of the span (1-based, inclusive). */ | ||
| "line_start": 2, | ||
| /* The last line number of the span (1-based, inclusive). */ | ||
| "line_end": 2, | ||
| /* The first character offset of the line_start (1-based, inclusive). */ | ||
| "column_start": 9, | ||
| /* The last character offset of the line_end (1-based, exclusive). */ | ||
| "column_end": 10, | ||
| /* Whether or not this is the "primary" span. | ||
| This indicates that this span is the focal point of the | ||
| diagnostic. | ||
| There are rare cases where multiple spans may be marked as | ||
| primary. For example, "immutable borrow occurs here" and | ||
| "mutable borrow ends here" can be two separate primary spans. | ||
| The top (parent) message should always have at least one | ||
| primary span, unless it has zero spans. Child messages may have | ||
| zero or more primary spans. | ||
| */ | ||
| "is_primary": true, | ||
| /* An array of objects showing the original source code for this | ||
| span. This shows the entire lines of text where the span is | ||
| located. A span across multiple lines will have a separate | ||
| value for each line. | ||
| */ | ||
| "text": [ | ||
| { | ||
| /* The entire line of the original source code. */ | ||
| "text": " let x = 123;", | ||
| /* The first character offset of the line of | ||
| where the span covers this line (1-based, inclusive). */ | ||
| "highlight_start": 9, | ||
| /* The last character offset of the line of | ||
| where the span covers this line (1-based, exclusive). */ | ||
| "highlight_end": 10 | ||
| } | ||
| ], | ||
| /* An optional message to display at this span location. | ||
| This is typically null for primary spans. | ||
| */ | ||
| "label": null, | ||
| /* An optional string of a suggested replacement for this span to | ||
| solve the issue. Tools may try to replace the contents of the | ||
| span with this text. | ||
| */ | ||
| "suggested_replacement": null, | ||
| /* An optional string that indicates the confidence of the | ||
| "suggested_replacement". Tools may use this value to determine | ||
| whether or not suggestions should be automatically applied. | ||
| Possible values may be: | ||
| - "MachineApplicable": The suggestion is definitely what the | ||
| user intended. This suggestion should be automatically | ||
| applied. | ||
| - "MaybeIncorrect": The suggestion may be what the user | ||
| intended, but it is uncertain. The suggestion should result | ||
| in valid Rust code if it is applied. | ||
| - "HasPlaceholders": The suggestion contains placeholders like | ||
| `(...)`. The suggestion cannot be applied automatically | ||
| because it will not result in valid Rust code. The user will | ||
| need to fill in the placeholders. | ||
| - "Unspecified": The applicability of the suggestion is unknown. | ||
| */ | ||
| "suggestion_applicability": null, | ||
| /* An optional object indicating the expansion of a macro within | ||
| this span. | ||
| If a message occurs within a macro invocation, this object will | ||
| provide details of where within the macro expansion the message | ||
| is located. | ||
| */ | ||
| "expansion": { | ||
| /* The span of the macro invocation. | ||
| Uses the same span definition as the "spans" array. | ||
| */ | ||
| "span": {/*...*/} | ||
| /* Name of the macro, such as "foo!" or "#[derive(Eq)]". */ | ||
| "macro_decl_name": "some_macro!", | ||
| /* Optional span where the relevant part of the macro is | ||
| defined. */ | ||
| "def_site_span": {/*...*/}, | ||
| } | ||
| } | ||
| ], | ||
| /* Array of attached diagnostic messages. | ||
| This is an array of objects using the same format as the parent | ||
| message. Children are not nested (children do not themselves | ||
| contain "children" definitions). | ||
| */ | ||
| "children": [ | ||
| { | ||
| "message": "`#[warn(unused_variables)]` on by default", | ||
| "code": null, | ||
| "level": "note", | ||
| "spans": [], | ||
| "children": [], | ||
| "rendered": null | ||
| }, | ||
| { | ||
| "message": "consider prefixing with an underscore", | ||
| "code": null, | ||
| "level": "help", | ||
| "spans": [ | ||
| { | ||
| "file_name": "lib.rs", | ||
| "byte_start": 21, | ||
| "byte_end": 22, | ||
| "line_start": 2, | ||
| "line_end": 2, | ||
| "column_start": 9, | ||
| "column_end": 10, | ||
| "is_primary": true, | ||
| "text": [ | ||
| { | ||
| "text": " let x = 123;", | ||
| "highlight_start": 9, | ||
| "highlight_end": 10 | ||
| } | ||
| ], | ||
| "label": null, | ||
| "suggested_replacement": "_x", | ||
| "suggestion_applicability": "MachineApplicable", | ||
| "expansion": null | ||
| } | ||
| ], | ||
| "children": [], | ||
| "rendered": null | ||
| } | ||
| ], | ||
| /* Optional string of the rendered version of the diagnostic as displayed | ||
| by rustc. Note that this may be influenced by the `--json` flag. | ||
| */ | ||
| "rendered": "warning: unused variable: `x`\n --> lib.rs:2:9\n |\n2 | let x = 123;\n | ^ help: consider prefixing with an underscore: `_x`\n |\n = note: `#[warn(unused_variables)]` on by default\n\n" | ||
| } | ||
| ``` | ||
|
|
||
| ## Artifact notifications | ||
|
|
||
| Artifact notifications are emitted when the [`--json=artifacts` | ||
| flag][option-json] is used. They indicate that a file artifact has been saved | ||
| to disk. More information about emit kinds may be found in the [`--emit` | ||
| flag][option-emit] documentation. | ||
|
|
||
| ```javascript | ||
| { | ||
| /* The filename that was generated. */ | ||
| "artifact": "libfoo.rlib", | ||
| /* The kind of artifact that was generated. Possible values: | ||
| - "link": The generated crate as specified by the crate-type. | ||
| - "dep-info": The `.d` file with dependency information in a Makefile-like syntax. | ||
| - "metadata": The Rust `.rmeta` file containing metadata about the crate. | ||
| - "save-analysis": A JSON file emitted by the `-Zsave-analysis` feature. | ||
| */ | ||
| "emit": "link" | ||
| } | ||
| ``` | ||
|
|
||
| [option-emit]: command-line-arguments.md#option-emit | ||
| [option-error-format]: command-line-arguments.md#option-error-format | ||
| [option-json]: command-line-arguments.md#option-json |