[haskell-servant][haskell-yesod] Fix specialCharReplacements

[msakai]

HaskellServantCodegen and HaskellYesodServerCodegen modify specialCharReplacements by replacing its keys: backslash (\) with \\ and " with \".

It seems that those replacements were for using the keys in string literals in the specialChars table in the generated code.
I.e. we want to have ("\\", "Back_Slash") instead of ("\", "Back_Slash") and ("\"", "Double_Quote") instead of (""", "Double_Quote") in the table below.

openapi-generator/samples/server/petstore/haskell-servant/lib/OpenAPIPetstore/Types.hs

Lines 158 to 196 in 81c398e

	specialChars =
	[ ("$", "Dollar")
	, ("^", "Caret")
	, ("|", "Pipe")
	, ("=", "Equal")
	, ("*", "Star")
	, ("-", "Dash")
	, ("&", "Ampersand")
	, ("%", "Percent")
	, ("#", "Hash")
	, ("@", "At")
	, ("!", "Exclamation")
	, ("+", "Plus")
	, (":", "Colon")
	, (";", "Semicolon")
	, (">", "GreaterThan")
	, ("<", "LessThan")
	, (".", "Period")
	, ("_", "Underscore")
	, ("?", "Question_Mark")
	, (",", "Comma")
	, ("'", "Quote")
	, ("/", "Slash")
	, ("(", "Left_Parenthesis")
	, (")", "Right_Parenthesis")
	, ("{", "Left_Curly_Bracket")
	, ("}", "Right_Curly_Bracket")
	, ("[", "Left_Square_Bracket")
	, ("]", "Right_Square_Bracket")
	, ("~", "Tilde")
	, ("`", "Backtick")
	, ("<=", "Less_Than_Or_Equal_To")
	, (">=", "Greater_Than_Or_Equal_To")
	, ("!=", "Not_Equal")
	, ("<>", "Not_Equal")
	, ("~=", "Tilde_Equal")
	, ("\\", "Back_Slash")
	, ("\"", "Double_Quote")
	]

However, modifying the keys causes the substitution of those characters in field names not to work, making generated code syntactically invalid. Suppose we have the following spec:

openapi: 3.0.0
info:
  title: Test
  description: Test API
  version: 1.0.0
servers:
  - url: https://api.example.com/
    description: the server

paths:
  /hello:
    get:
      operationId: hello
      summary: "summary"
      description: "description."
      responses:
        "200":
          description: foo
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HelloResponse'

components:
  schemas:
    HelloResponse:
      type: object
      properties:
        "\"":
          type: string
          description: double quote
        "\\":
          type: string
          description: backslash
      required:
        - "\""
        - "\\"
      description: description

Those generators generate the following data type definition, but helloResponse" and helloResponse\ are invalid identifiers in Haskell.

-- | description
data HelloResponse = HelloResponse
  { helloResponse" :: Text -- ^ double quote
  , helloResponse\ :: Text -- ^ backslash
  } deriving (Show, Eq, Generic, Data)

Since the specialChars table has already been removed in #16232, we can safely stop modifying the specialCharReplacements, thereby generated code for the above example become the following syntactically correct code.

-- | description
data HelloResponse = HelloResponse
  { helloResponseDoubleQuote :: Text -- ^ double quote
  , helloResponseBackSlash :: Text -- ^ backslash
  } deriving (Show, Eq, Generic, Data)

I believe that this change maintains backward compatibility, as it only fixes cases where it has not been working (when field names contain backslashes or double quotes).

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  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

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  ./bin/utils/ensure-up-to-date
  

  Commit all changed files.
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[wing328]

Tested locally to confirm both the issue and the fix. Thanks for the PR.

➜  haskell-servant stack test
test> configure (lib)
Configuring test-0.1.0.0...
test> build (lib)
Preprocessing library for test-0.1.0.0..
Building library for test-0.1.0.0..
[1 of 2] Compiling Test.Types

/private/tmp/haskell-servant/lib/Test/Types.hs:29:45: error:
    lexical error in string/character literal at character '\n'
   |
29 |   { helloResponse" :: Text -- ^ double quote
   |                                             ^

--  While building package test-0.1.0.0 (scroll up to its section to see the error) using:
      /Users/williamcheng/.stack/setup-exe-cache/x86_64-osx/Cabal-simple_mPHDZzAJ_3.4.1.0_ghc-9.0.2 --builddir=.stack-work/dist/x86_64-osx/Cabal-3.4.1.0 build lib:test --ghc-options " -fdiagnostics-color=always"
    Process exited with code: ExitFailure 1
➜  haskell-servant stack test
test> configure (lib)
Configuring test-0.1.0.0...
test> build (lib)
Preprocessing library for test-0.1.0.0..
Building library for test-0.1.0.0..
[1 of 2] Compiling Test.Types
[2 of 2] Compiling Test.API
test> copy/register
Installing library in /private/tmp/haskell-servant/.stack-work/install/x86_64-osx/d7eaccd255e546d469fd16f5af3892ff7caa92ed8e070d4c3bfe612e97b830c4/9.0.2/lib/x86_64-osx-ghc-9.0.2/test-0.1.0.0-AJ8CDUTcGyD9fnQsiG31e2
Registering library for test-0.1.0.0..
➜  haskell-servant 

I'll file a separate PR to add some tests.

[wing328]

Merged #16290 to add some tests and github workflow.