Motion 
Motion is a tool that was designed to work with editors. It is providing contextual information for a given offset(option) from a file or directory of files. Editors can use these informations to implement navigation, text editing, etc... that are specific to a Go source code.
It's optimized and created to work with vim-go, but it's designed to work with any editor. It's currently work in progress and open to change.
Install
go get github.com/fatih/motionUsage
motion is meant to be run via the editor. Currently it has the following
modes you can use:
decls: returns a list of declarations based on the-includeflagenclosing: returns information about the enclosing function for a given offsetnext: returns the next function information for a given offsetprev: returns the previous function information for a given offsetcomment: returns information about the a comment block (if any).
A function information is currently the following type definition (defined as
astcontext.Func):
type Func struct {
// Signature of the function
Signature *FuncSignature `json:"sig" vim:"sig"`
// position of the "func" keyword
FuncPos *Position `json:"func" vim:"func"`
Lbrace *Position `json:"lbrace" vim:"lbrace"` // position of "{"
Rbrace *Position `json:"rbrace" vim:"rbrace"` // position of "}"
// position of the doc comment, only for *ast.FuncDecl
Doc *Position `json:"doc,omitempty" vim:"doc,omitempty"`
node ast.Node // either *ast.FuncDecl or *ast.FuncLit
}
motion can output the information currently in formats: json and vim.
An example execution for the enclosing mode and output in json format is:
$ motion -file testdata/main.go -offset 180 -mode enclosing --format json
{
"mode": "enclosing",
"func": {
"sig": {
"full": "func Bar() (string, error)",
"recv": "",
"name": "Bar",
"in": "",
"out": "string, error"
},
"func": {
"filename": "testdata/main.go",
"offset": 174,
"line": 15,
"col": 1
},
"lbrace": {
"filename": "testdata/main.go",
"offset": 201,
"line": 15,
"col": 28
},
"rbrace": {
"filename": "testdata/main.go",
"offset": 225,
"line": 17,
"col": 1
}
}
}
To include the doc comments for function declarations include the
--parse-comments flag:
$ motion -file testdata/main.go -offset 180 -mode enclosing --format json --parse-comments
{
"mode": "enclosing",
"func": {
"sig": {
"full": "func Bar() (string, error)",
"recv": "",
"name": "Bar",
"in": "",
"out": "string, error"
},
"func": {
"filename": "testdata/main.go",
"offset": 174,
"line": 15,
"col": 1
},
"lbrace": {
"filename": "testdata/main.go",
"offset": 201,
"line": 15,
"col": 28
},
"rbrace": {
"filename": "testdata/main.go",
"offset": 225,
"line": 17,
"col": 1
},
"doc": {
"filename": "testdata/main.go",
"offset": 134,
"line": 14,
"col": 1
}
}
}
For example the same query, but with mode -mode next returns a different
result. Instead it returns the next function inside the source code:
$ motion -file testdata/main.go -offset 180 -mode next --format json
{
"mode": "next",
"func": {
"sig": {
"full": "func example() error",
"recv": "",
"name": "example",
"in": "",
"out": "error"
},
"func": {
"filename": "testdata/main.go",
"offset": 318,
"line": 21,
"col": 1
},
"lbrace": {
"filename": "testdata/main.go",
"offset": 339,
"line": 21,
"col": 22
},
"rbrace": {
"filename": "testdata/main.go",
"offset": 402,
"line": 29,
"col": 1
}
}
}
If there are not functions available for any mode, it returns an error in the specified format:
$ motion -file testdata/main.go -offset 330 -mode next --format json
{
"err": "no functions found"
}
For the mode decls, we pass the file (you can also pass a directory)
and instruct to only include function declarations with the -include func
flag:
$ motion -file testdata/main.go -mode decls -include func
{
"mode": "decls",
"decls": [
{
"keyword": "func",
"ident": "main",
"full": "func main()",
"filename": "testdata/main.go",
"line": 9,
"col": 1
},
{
"keyword": "func",
"ident": "Bar",
"full": "func Bar() (string, error)",
"filename": "testdata/main.go",
"line": 15,
"col": 1
},
{
"keyword": "func",
"ident": "example",
"full": "func example() error",
"filename": "testdata/main.go",
"line": 21,
"col": 1
}
]
}
In the comment mode it will try to get information about the comment block for
a given offset:
$ motion -mode comment -file ./vim/vim.go -offset 3
{
"mode": "comment",
"comment": {
"startLine": 1,
"startCol": 1,
"endLine": 3,
"endCol": 50
}
}