How to automatically re-indent a YAML file? -

let's consider example:

--- foo:   alice: female   bob:   male bar:   - node: 42     name: none   - node: 43     name: none 

if decide reindent , start this:

--- foo: alice: female bob:   male bar: - node: 42 name: none - node: 43 name: none 

i don't have enough information it. vim's attempt this:

--- foo:     alice: female bob:   male bar:     - node: 42 name: none - node: 43 name: none 

ansible cannot make well:

--- foo:  alice: female bob:   male bar:  - node: 42   name: none   - node: 43     name: none 

i think possible workaround add blank line when indentation increased:

--- foo:    alice: female   bob:   male bar:    - node: 42     name: none   - node: 43     name: none 

in opinion, main problem yaml people still fighting tabs, spaces , indent size. large yaml files edited several people, resulting file cannot parsed anymore. 2 solutions see are:

1. use tabs , force tabs identation case makefiles
2. the above solution

what seem want making sure yaml files uniformly indented (e.g. before being checked revision control system). idea of dedenting , re-indenting not work lose information if flatten structure. this:

foo:   alice: female   bob:   male 

consists of 2 mappings: mapping 1 key , value mapping of 2 keys 2 values.

this:

foo: alice: female bob:   male 

is 1 mapping 3 keys, , key foo has value null scalar (also writable, apart empty string, ~, null, null in yaml files).

most yaml parsers lose information when reading in file internal data: - comments dropped - key ordering not preserved mappings - spaces around scalars not preserved

the ruamel.yaml python package (of author) enhancemed parser allows round-tripping yaml file data , yaml preserve more of original information. preserve comments , key ordering, drops e.g. spacing around single line scalars.

this round-tripping stabilizes on second round-trip , can used reindent yaml file. yaml utility included in package can used without need program things yourself:

yaml round-trip your_file.yml --verbose 

(round-trip can shortened rt) check whether , how file change. shows unified diff if change. based on can decide save file if stabilizes:

yaml round-trip your_file.yml --save 

the output example.yml:

--- foo:   alice: female  # verified   bob:   male bar: - node:   42   name: none -     node: 43       name: none 

would be:

example.yml:      stabilzes on second round trip, ok without comments --- example.yml +++ round trip yaml @@ -1,9 +1,9 @@  ---  foo:    alice: female  # verified -  bob:   male +  bob: male  bar: -- node:   42 +- node: 42    name: none --     node: 43 -      name: none +- node: 43 +  name: none 

and when saved like:

--- foo:   alice: female  # verified   bob: male bar: - node: 42   name: none - node: 43   name: none 

the indentation level default 2, can set option yaml.