RFC: Default value validation & coercion (graphql#3814)

[graphql#3049 rebased on
main](graphql#3049).

This is the last rebased PR from the original PR stack concluding with
graphql#3049.

* Rebased: graphql#3809 [Original: graphql#3092]
* Rebased: graphql#3810 [Original: graphql#3074]
* Rebased: graphql#3811 [Original: graphql#3077]
* Rebased: graphql#3812 [Original: graphql#3065]
* Rebased: graphql#3813 [Original: graphql#3086]
* Rebased: graphql#3814 (this PR) [Original: graphql#3049]

Update: graphql#3044 and graphql#3145 have been separated from this stack.

Changes from original PR:
1. `astFromValue()` is deprecated instead of being removed.

@leebyron comments from graphql#3049, the original PR:
> Implements
[graphql/graphql-spec#793](graphql/graphql-spec#793)
> 
> * BREAKING: Changes default values from being represented as an
assumed-coerced "internal input value" to a pre-coerced "external input
value" (See chart below).
> This allows programmatically provided default values to be represented
in the same domain as values sent to the service via variable values,
and allows it to have well defined methods for both transforming into a
printed GraphQL literal string for introspection / schema printing (via
`valueToLiteral()`) or coercing into an "internal input value" for use
at runtime (via `coerceInputValue()`)
> To support this change in value type, this PR adds two related
behavioral changes:
>   
> * Adds coercion of default values from external to internal at runtime
(within `coerceInputValue()`)
> * Removes `astFromValue()`, replacing it with `valueToLiteral()` for
use in introspection and schema printing. `astFromValue()` performed
unsafe "uncoercion" to convert an "Internal input value" directly to a
"GraphQL Literal AST", where `valueToLiteral()` performs a well defined
transform from "External input value" to "GraphQL Literal AST".
> * Adds validation of default values during schema validation.
> Since assumed-coerced "internal" values may not pass "external"
validation (for example, Enum values), an additional validation error
has been included which attempts to detect this case and report a
strategy for resolution.
> 
> Here's a broad overview of the intended end state:
> 
> ![GraphQL Value
Flow](https://user-images.githubusercontent.com/50130/118379946-51ac5300-b593-11eb-839f-c483ecfbc875.png)

---------

Co-authored-by: Lee Byron <lee@leebyron.com>

Author: yaacovCR

cspell.yml

@@ -35,6 +35,8 @@ words:
   - Coodinate
   - metafield
   - graphiql
+  - uncoerce
+  - uncoerced
 
   # Different names used inside tests
   - Skywalker

src/execution/__tests__/variables-test.ts

@@ -150,7 +150,6 @@ const TestType = new GraphQLObjectType({
     }),
     fieldWithNestedInputObject: fieldWithInputArg({
       type: TestNestedInputObject,
-      defaultValue: 'Hello World',
     }),
     list: fieldWithInputArg({ type: new GraphQLList(GraphQLString) }),
     nested: {

src/index.ts

@@ -443,6 +443,7 @@ export {
   // Create a JavaScript value from a GraphQL language AST without a Type.
   valueFromASTUntyped,
   // Create a GraphQL language AST from a JavaScript value.
+  /** @deprecated use `valueToLiteral()` instead with care to operate on external values - `astFromValue()` will be removed in v18 */
   astFromValue,
   // A helper to use within recursive-descent visitors which need to be aware of the GraphQL type system.
   TypeInfo,

src/type/__tests__/enumType-test.ts

@@ -71,9 +71,7 @@ const QueryType = new GraphQLObjectType({
       args: {
         fromEnum: {
           type: ComplexEnum,
-          // Note: defaultValue is provided an *internal* representation for
-          // Enums, rather than the string name.
-          defaultValue: Complex1,
+          defaultValue: 'ONE',
         },
         provideGoodValue: { type: GraphQLBoolean },
         provideBadValue: { type: GraphQLBoolean },