-- in flag names causes parsing failure

[ivan-m]

General summary/comments (optional)

Trying to specify a flag with -- in the name in stack.yaml causes a parsing failure.

Steps to reproduce

1. Have this stack.yaml (note that this is valid YAML: I've tried various syntax checkers/linters and they have no problem with the --):

   resolver: lts-8.9
   extra-deps:
      - cassava-0.5.1.0
      - Only-0.1
      - text-short-0.1
   flags:
     cassava:
       bytestring--LT-0_10_4: false

2. stack ide targets

Expected

List of targets is printed

Actual

Could not parse 'stack.yaml':
Aeson exception:
Error in $.flags.cassava['bytestring--LT-0_10_4']: failed to parse field 'flags': Invalid flag name: "bytestring--LT-0_10_4"
See http://docs.haskellstack.org/en/stable/yaml_configuration/

Removing the -- solves the issue, so there must be something to do with those double dashes.

Related: haskell-hvr/cassava#157

Stack version

$ stack --version
Version 1.5.1 x86_64
Compiled with:
- Cabal-1.24.2.0
- Glob-0.8.0
- HUnit-1.5.0.0
- MonadRandom-0.5.1
- QuickCheck-2.9.2
- SHA-1.6.4.2
- StateVar-1.1.0.4
- aeson-1.1.2.0
- aeson-compat-0.3.6
- annotated-wl-pprint-0.7.0
- ansi-terminal-0.6.3.1
- ansi-wl-pprint-0.6.7.3
- array-0.5.1.1
- asn1-encoding-0.9.5
- asn1-parse-0.9.4
- asn1-types-0.3.2
- async-2.1.1.1
- attoparsec-0.13.1.0
- attoparsec-iso8601-1.0.0.0
- auto-update-0.1.4
- base-4.9.1.0
- base-compat-0.9.3
- base-orphans-0.6
- base16-bytestring-0.1.1.6
- base64-bytestring-1.0.0.1
- basement-0.0.2
- bifunctors-5.4.2
- binary-0.8.3.0
- binary-tagged-0.1.4.2
- bitarray-0.0.1.1
- blaze-builder-0.4.0.2
- blaze-html-0.9.0.1
- blaze-markup-0.8.0.0
- byteable-0.1.1
- bytestring-0.10.8.1
- call-stack-0.1.0
- case-insensitive-1.2.0.10
- cereal-0.5.4.0
- clock-0.7.2
- comonad-5.0.2
- conduit-1.2.12
- conduit-extra-1.1.17
- connection-0.2.8
- constraints-0.9.1
- containers-0.5.7.1
- contravariant-1.4
- cookie-0.4.2.1
- cryptohash-0.11.9
- cryptohash-sha256-0.11.100.1
- cryptonite-0.23
- cryptonite-conduit-0.2.0
- data-default-class-0.1.2.0
- deepseq-1.4.2.0
- digest-0.0.1.2
- directory-1.3.0.0
- distributive-0.5.3
- dlist-0.8.0.3
- easy-file-0.2.1
- echo-0.1.3
- ed25519-0.0.5.0
- either-4.4.1.1
- errors-2.2.2
- exceptions-0.8.3
- extra-1.5.3
- fail-4.9.0.0
- fast-logger-2.4.10
- file-embed-0.0.10
- filelock-0.1.1.2
- filepath-1.4.1.1
- foundation-0.0.15
- free-4.12.4
- fsnotify-0.2.1.1
- generic-deriving-1.11.2
- generics-sop-0.3.1.0
- ghc-boot-th-8.0.2
- ghc-prim-0.5.0.0
- gitrev-1.3.1
- hackage-security-0.5.2.2
- hashable-1.2.6.1
- hastache-0.6.1
- hfsevents-0.1.6
- hourglass-0.2.10
- hpack-0.19.1
- hpc-0.6.0.3
- hspec-2.4.4
- hspec-core-2.4.4
- hspec-discover-2.4.4
- hspec-expectations-0.8.2
- hspec-smallcheck-0.4.2
- http-api-data-0.3.7.1
- http-client-0.5.7.0
- http-client-tls-0.3.5.1
- http-conduit-2.2.3.2
- http-types-0.9.1
- ieee754-0.8.0
- integer-gmp-1.0.0.1
- integer-logarithms-1.0.2
- lifted-async-0.9.3
- lifted-base-0.2.3.11
- logict-0.6.0.2
- memory-0.14.8
- microlens-0.4.8.1
- microlens-mtl-0.1.11.0
- microlens-th-0.4.1.1
- mime-types-0.1.0.7
- mintty-0.1.1
- mmorph-1.0.9
- monad-control-1.0.2.2
- monad-logger-0.3.25.1
- monad-loops-0.4.3
- monad-unlift-0.2.0
- mono-traversable-1.0.2.1
- mtl-2.2.1
- nats-1.1.1
- network-2.6.3.2
- network-uri-2.6.1.0
- old-locale-1.0.0.7
- old-time-1.1.0.3
- open-browser-0.2.1.0
- optparse-applicative-0.13.2.0
- optparse-simple-0.0.3
- parsec-3.1.11
- path-0.5.13
- path-io-1.2.2
- path-pieces-0.2.1
- pem-0.2.2
- persistent-2.7.0
- persistent-sqlite-2.6.2
- persistent-template-2.5.2
- pid1-0.1.2.0
- prelude-extras-0.4.0.3
- pretty-1.1.3.3
- primitive-0.6.2.0
- process-1.4.3.0
- profunctors-5.2.1
- project-template-0.2.0
- quickcheck-io-0.2.0
- random-1.1
- regex-applicative-0.3.3
- regex-applicative-text-0.1.0.1
- resource-pool-0.2.3.2
- resourcet-1.1.9
- retry-0.7.4.2
- rts-1.0
- safe-0.3.15
- safe-exceptions-0.1.6.0
- scientific-0.3.5.2
- semigroupoids-5.2.1
- semigroups-0.18.3
- setenv-0.1.1.3
- silently-1.2.5
- smallcheck-1.1.2
- socks-0.5.5
- split-0.2.3.2
- stm-2.4.4.1
- stm-chans-3.0.0.4
- store-0.4.3.2
- store-core-0.4.1
- streaming-commons-0.1.17
- syb-0.7
- tagged-0.8.5
- tar-0.5.0.3
- template-haskell-2.11.1.0
- temporary-1.2.1.1
- text-1.2.2.2
- text-binary-0.2.1.1
- text-metrics-0.3.0
- tf-random-0.5
- th-expand-syns-0.4.3.0
- th-lift-0.7.7
- th-lift-instances-0.1.11
- th-orphans-0.13.4
- th-reify-many-0.1.8
- th-utilities-0.2.0.1
- time-1.6.0.1
- time-locale-compat-0.1.1.3
- tls-1.3.11
- transformers-0.5.2.0
- transformers-base-0.4.4
- transformers-compat-0.5.1.4
- unexceptionalio-0.3.0
- unicode-transforms-0.3.3
- unix-2.7.2.1
- unix-compat-0.4.3.1
- unix-time-0.3.7
- unordered-containers-0.2.8.0
- uri-bytestring-0.2.3.3
- uuid-types-1.0.3
- vector-0.12.0.1
- vector-algorithms-0.7.0.1
- vector-binary-instances-0.2.3.5
- void-0.7.2
- x509-1.7.2
- x509-store-1.6.5
- x509-system-1.6.6
- x509-validation-1.6.9
- yaml-0.8.23.3
- zip-archive-0.3.1.1
- zlib-0.6.1.2

Method of installation

• Installed via Nix on macOS.

[ivan-m]

This isn't a problem with parsing the YAML as it succeeds:

Prelude Data.Yaml> decodeFileEither "test.yaml" :: IO (Either ParseException Value )
Right (Object (fromList [("flags",Object (fromList [("cassava",Object (fromList [("bytestring--LT-0_10_4",Bool False)]))])),("extra-deps",Array [String "cassava-0.5.1.0",String "Only-0.1",String "text-short-0.1"]),("resolver",String "lts-8.9")]))

[ivan-m]

This appears to be a duplicate of #3345, which has already been resolved.