## errorformat - Vim 'errorformat' implementation in Go

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errorformat is Vim's quickfix [errorformat](https://vim-jp.org/vimdoc-en/quickfix.html#error-file-format) implementation in golang.

errorformat provides default errorformats for major tools.
You can see defined errorformats [here](https://godoc.org/github.com/reviewdog/errorformat/fmts).
Also, it's easy to [add new errorformat](fmts/README.md) in a similar way to Vim's errorformat.

Note that it's highly compatible with Vim implementation, but it doesn't support Vim regex.

### :arrow_forward: Playground :arrow_forward:

Try errorformat on [the Playground](https://reviewdog.github.io/errorformat-playground/)!

The playground uses [gopherjs](https://github.com/gopherjs/gopherjs) to try
errorformat implementation in Go with JavaScript :sparkles:

### Usage

```go
import "github.com/reviewdog/errorformat"
```

### Example

#### Code:

```go
in := `
golint.new.go:3:5: exported var V should have comment or be unexported
golint.new.go:5:5: exported var NewError1 should have comment or be unexported
golint.new.go:7:1: comment on exported function F should be of the form "F ..."
golint.new.go:11:1: comment on exported function F2 should be of the form "F2 ..."
`
efm, _ := errorformat.NewErrorformat([]string{`%f:%l:%c: %m`, `%-G%.%#`})
s := efm.NewScanner(strings.NewReader(in))
for s.Scan() {
    fmt.Println(s.Entry())
}
```

#### Output:

```
golint.new.go|3 col 5| exported var V should have comment or be unexported
golint.new.go|5 col 5| exported var NewError1 should have comment or be unexported
golint.new.go|7 col 1| comment on exported function F should be of the form "F ..."
golint.new.go|11 col 1| comment on exported function F2 should be of the form "F2 ..."
```

### CLI tool

#### Installation

```
go get -u github.com/reviewdog/errorformat/cmd/errorformat
```

#### Usage

```
Usage: errorformat [flags] [errorformat ...]

errorformat reads compiler/linter/static analyzer result from STDIN, formats
them by given 'errorformat' (90% compatible with Vim's errorformat. :h
errorformat), and outputs formated result to STDOUT.

Example:
        $ echo '/path/to/file:14:28: error message\nfile2:3:4: msg' | errorformat "%f:%l:%c: %m"
        /path/to/file|14 col 28| error message
        file2|3 col 4| msg

        $ golint ./... | errorformat -name=golint

The -f flag specifies an alternate format for the entry, using the
syntax of package template.  The default output is equivalent to -f
'{{.String}}'. The struct being passed to the template is:

        type Entry struct {
                // name of a file
                Filename string
                // line number
                Lnum int
                // column number (first column is 1)
                Col int
                // true: "col" is visual column
                // false: "col" is byte index
                Vcol bool
                // error number
                Nr int
                // search pattern used to locate the error
                Pattern string
                // description of the error
                Text string
                // type of the error, 'E', '1', etc.
                Type rune
                // true: recognized error message
                Valid bool

                // Original error lines (often one line. more than one line for multi-line
                // errorformat. :h errorformat-multi-line)
                Lines []string
        }

Flags:
  -f string
        format template for -w=template (default "{{.String}}")
  -list
        list defined errorformats
  -name string
        defined errorformat name
  -sarif.tool-name string
        Tool name for Sarif writer format. Use -name flag if available.
  -w string
        writer format (template|checkstyle|jsonl|sarif) (default "template")
```

```
$ cat testdata/sbt.in
[warn] /path/to/F1.scala:203: local val in method f is never used: (warning smaple 3)
[warn]         val x = 1
[warn]             ^
[warn] /path/to/F1.scala:204: local val in method f is never used: (warning smaple 2)
[warn]   val x = 2
[warn]       ^
[error] /path/to/F2.scala:1093: error: value ++ is not a member of Int
[error]     val x = 1 ++ 2
[error]               ^
[warn] /path/to/dir/F3.scala:83: local val in method f is never used
[warn]         val x = 4
[warn]             ^
[error] /path/to/dir/F3.scala:84: error: value ++ is not a member of Int
[error]         val x = 5 ++ 2
[error]                   ^
[warn] /path/to/dir/F3.scala:86: local val in method f is never used
[warn]         val x = 6
[warn]             ^
$ errorformat "%E[%t%.%+] %f:%l: error: %m" "%A[%t%.%+] %f:%l: %m" "%Z[%.%+] %p^" "%C[%.%+] %.%#" "%-G%.%#" < testdata/sbt.in
/path/to/F1.scala|203 col 13 warning| local val in method f is never used: (warning smaple 3)
/path/to/F1.scala|204 col 7 warning| local val in method f is never used: (warning smaple 2)
/path/to/F2.scala|1093 col 15 error| value &#43;&#43; is not a member of Int
/path/to/dir/F3.scala|83 col 13 warning| local val in method f is never used
/path/to/dir/F3.scala|84 col 19 error| value &#43;&#43; is not a member of Int
/path/to/dir/F3.scala|86 col 13 warning| local val in method f is never used
$ cat fmts/testdata/sbt.in | errorformat -name=sbt -w=checkstyle
<?xml version="1.0" encoding="UTF-8"?>
<checkstyle version="1.0">
  <file name="/home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala">
    <error column="3" line="6" message="missing argument list for method error in object Predef" severity="error"></error>
    <error column="15" line="4" message="private val in object F is never used" severity="warning"></error>
    <error column="15" line="5" message="private method in object F is never used" severity="warning"></error>
  </file>
</checkstyle>
$ cat fmts/testdata/sbt.in | errorformat -name=sbt -w=jsonl
{"filename":"/home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala","lnum":6,"col":3,"vcol":true,"nr":0,"pattern":"","text":"missing argument list for method error in object Predef","type":101,"valid":true,"lines":["[error] /home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala:6: missing argument list for method error in object Predef","[error] Unapplied methods are only converted to functions when a function type is expected.","[error] You can make this conversion explicit by writing `error _` or `error(_)` instead of `error`.","[error]   error","[error]   ^"]}
{"filename":"/home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala","lnum":4,"col":15,"vcol":true,"nr":0,"pattern":"","text":"private val in object F is never used","type":119,"valid":true,"lines":["[warn] /home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala:4: private val in object F is never used","[warn]   private val unused = 1","[warn]               ^"]}
{"filename":"/home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala","lnum":5,"col":15,"vcol":true,"nr":0,"pattern":"","text":"private method in object F is never used","type":119,"valid":true,"lines":["[warn] /home/haya14busa/src/github.com/reviewdog/errorformat/fmts/testdata/resources/scala/scalac.scala:5: private method in object F is never used","[warn]   private def unusedF = {}","[warn]               ^"]}
```

### SARIF Support (experimental)

It supports [SARIF](https://sarifweb.azurewebsites.net/) (Static Analysis Results Interchange Format) as output experimentally. Use `-w=sarif` to give it a shot.

<details>
<summary> Example: errorformat -w=sarif</summary>

```shell
$ cat fmts/testdata/sbt.in | errorformat -name=sbt -w=sarif
{
  "$schema": "http://json.schemastore.org/sarif-2.1.0-rtm.4",
  "runs": [
    {
      "results": [
        {
          "level": "error",
          "locations": [
            {
              "physicalLocation": {
                "artifactLocation": {
                  "uri": "fmts/testdata/resources/scala/scalac.scala",
                  "uriBaseId": "%SRCROOT%"
                },
                "region": {
                  "startColumn": 3,
                  "startLine": 6
                }
              }
            }
          ],
          "message": {
            "text": "missing argument list for method error in object Predef"
          }
        },
        {
          "level": "warning",
          "locations": [
            {
              "physicalLocation": {
                "artifactLocation": {
                  "uri": "fmts/testdata/resources/scala/scalac.scala",
                  "uriBaseId": "%SRCROOT%"
                },
                "region": {
                  "startColumn": 15,
                  "startLine": 4
                }
              }
            }
          ],
          "message": {
            "text": "private val in object F is never used"
          }
        },
        {
          "level": "warning",
          "locations": [
            {
              "physicalLocation": {
                "artifactLocation": {
                  "uri": "fmts/testdata/resources/scala/scalac.scala",
                  "uriBaseId": "%SRCROOT%"
                },
                "region": {
                  "startColumn": 15,
                  "startLine": 5
                }
              }
            }
          ],
          "message": {
            "text": "private method in object F is never used"
          }
        }
      ],
      "tool": {
        "driver": {
          "name": "sbt"
        }
      }
    }
  ],
  "version": "2.1.0"
}
```

</details>

### Use cases of 'errorformat' outside Vim

- [reviewdog/reviewdog - A code review dog who keeps your codebase healthy](https://github.com/haya14busa/reviewdog)
- [mattn/efm-langserver - General purpose Language Server](https://github.com/mattn/efm-langserver)

### :bird: Author

haya14busa (https://github.com/haya14busa)

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