Add builtin scalar helpers and improve hover tooltip infrastructure

- Add BUILTIN_SCALAR_NAMES constant and is_builtin_scalar_name() function
  to schema crate for consistent builtin scalar handling
- Update schema-set to use BUILTIN_SCALAR_NAMES instead of hardcoded list
- Add TruncatedPrinter with print_field() and print_type_truncated() functions
  to schema-print crate for hover tooltip SDL generation
- Add "..." truncation indicator when type definitions are truncated
- Add module docblock documenting hover tooltip format conventions
- Simplify Client Schema Extension hover message to always show Relay docs link

Author: captbaritone

compiler/crates/relay-lsp/src/hover/with_resolution_path.rs

@@ -5,6 +5,25 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+//! # Hover Tooltip Format
+//!
+//! Hover tooltips display information in this order:
+//!
+//! 1. Description: Human-readable description of the element (if available)
+//!
+//! 2. SDL Definition: GraphQL SDL syntax showing the element's signature
+//!    (e.g., `name(arg: String!): ID!` for fields, `type User { ... }` for types)
+//!
+//! 3. Type Link: Clickable link to the referenced type in the schema explorer,
+//!    with the type's description if available. Always shown for fields (even
+//!    without a type description). Omitted for built-in scalars
+//!    (`String`, `Int`, `Float`, `Boolean`, `ID`).
+//!
+//! 4. Documentation Links: Links to relevant documentation (e.g., Relay Resolver,
+//!    Client Schema Extension).
+//!
+//! 5. Source Links: Links to source code locations (e.g., Hack source).
+
 use common::DirectiveName;
 use common::NamedItem;
 use docblock_shared::RELAY_RESOLVER_DIRECTIVE_NAME;
@@ -875,17 +894,10 @@ fn get_scalar_or_linked_field_hover_content(
     }
 
     if is_resolver {
-        let msg = "**Relay Resolver**: This field is backed by a Relay Resolver, and is therefore only avaliable in Relay code. [Learn More](https://relay.dev/docs/guides/relay-resolvers/introduction/).";
+        let msg = "**Relay Resolver**: [Learn More](https://relay.dev/docs/guides/relay-resolvers/introduction/)";
         hover_contents.push(MarkedString::String(msg.to_string()))
     } else if field.is_extension {
-        let msg = match content_consumer_type {
-            ContentConsumerType::Relay => {
-                "**Client Schema Extension**: This field was declared as a Relay Client Schema Extension, and is therefore only avalaible in Relay code. [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions)."
-            }
-            ContentConsumerType::GraphQL => {
-                "**Client Schema Extension**: This field was declared as a GraphQL client schema extension explicitly among [these](https://fburl.com/code/9qg1gghd) files etc."
-            }
-        };
+        let msg = "**Client Schema Extension**: [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions)";
         hover_contents.push(MarkedString::String(msg.to_string()))
     }
 

compiler/crates/relay-lsp/tests/hover/fixtures/directive_alias.expected

@@ -0,0 +1,19 @@
+==================================== INPUT ====================================
+query MyQuery {
+  node(id: "123") {
+    ... on User @ali|as(as: "myUser") {
+      name
+    }
+  }
+}
+==================================== OUTPUT ===================================
+(Relay Only)
+
+Exposes a fragment's data as a new field which can be null checked to ensure it
+matches the parent selection.
+
+[Read More](https://relay.dev/docs/guides/alias-directive/)
+--
+```graphql
+directive @alias(as: String) on FRAGMENT_SPREAD | INLINE_FRAGMENT
+```

compiler/crates/relay-lsp/tests/hover/fixtures/directive_alias.graphql

@@ -0,0 +1,7 @@
+query MyQuery {
+  node(id: "123") {
+    ... on User @ali|as(as: "myUser") {
+      name
+    }
+  }
+}

compiler/crates/relay-lsp/tests/hover/fixtures/directive_required.expected

@@ -0,0 +1,19 @@
+==================================== INPUT ====================================
+query MyQuery {
+  me {
+    name @requ|ired(action: THROW)
+  }
+}
+==================================== OUTPUT ===================================
+(Relay Only)
+
+`@required` is a directive you can add to fields in your Relay queries to
+declare how null values should be handled at runtime. You can think of it as
+saying "if this field is ever null, its parent field is invalid and should be
+null".
+
+[Read More](https://relay.dev/docs/guides/required-directive/)
+--
+```graphql
+directive @required(action: RequiredFieldAction! @static) on FIELD
+```

compiler/crates/relay-lsp/tests/hover/fixtures/directive_required.graphql

@@ -0,0 +1,5 @@
+query MyQuery {
+  me {
+    name @requ|ired(action: THROW)
+  }
+}

compiler/crates/relay-lsp/tests/hover/fixtures/directive_throwOnFieldError.expected

@@ -0,0 +1,20 @@
+==================================== INPUT ====================================
+query MyQuery @throwOnFiel|dError {
+  me {
+    name
+  }
+}
+==================================== OUTPUT ===================================
+(Relay only)
+
+A directive added to queries and fragments which causes the Relay client to throw
+if reading a field that has an error. Relay will also honor the @semanticNonNull
+directive on fields read from that query or fragment. Emitted types for such
+fields will be non-null. Requires the `experimental_emit_semantic_nullability_types`
+typegen configuration to be enabled.
+
+[Read More](https://relay.dev/docs/api-reference/graphql-and-directives/)
+--
+```graphql
+directive @throwOnFieldError on QUERY | FRAGMENT_DEFINITION
+```

compiler/crates/relay-lsp/tests/hover/fixtures/directive_throwOnFieldError.graphql

@@ -0,0 +1,5 @@
+query MyQuery @throwOnFiel|dError {
+  me {
+    name
+  }
+}

compiler/crates/relay-lsp/tests/hover/fixtures/double_underscore_id_field.expected

@@ -11,4 +11,4 @@ Relay's cache key for this object.
 --
 Type: **[ID!](command:nuclide.relay-lsp.openSchemaExplorer?{%22path%22:[%22Query%22,%22User%22,%22ID%22],%22schemaName%22:%22Some%20Schema%20Name%22})**
 --
-**Client Schema Extension**: This field was declared as a Relay Client Schema Extension, and is therefore only avalaible in Relay code. [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions).
+**Client Schema Extension**: [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions)

compiler/crates/relay-lsp/tests/hover/fixtures/scalar_field_from_client_schema_extension.expected

@@ -20,4 +20,4 @@ This is a client schema field
 --
 Type: **[Int](command:nuclide.relay-lsp.openSchemaExplorer?{%22path%22:[%22Query%22,%22User%22,%22Int%22],%22schemaName%22:%22Some%20Schema%20Name%22})**
 --
-**Client Schema Extension**: This field was declared as a Relay Client Schema Extension, and is therefore only avalaible in Relay code. [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions).
+**Client Schema Extension**: [Learn More](https://relay.dev/docs/guided-tour/updating-data/client-only-data/#client-only-data-client-schema-extensions)

compiler/crates/relay-lsp/tests/hover/fixtures/scalar_field_from_relay_resolver.expected

@@ -21,4 +21,4 @@ My Resolver Description
 --
 Type: **[RelayResolverValue](command:nuclide.relay-lsp.openSchemaExplorer?{%22path%22:[%22Query%22,%22User%22,%22RelayResolverValue%22],%22schemaName%22:%22Some%20Schema%20Name%22})**
 --
-**Relay Resolver**: This field is backed by a Relay Resolver, and is therefore only avaliable in Relay code. [Learn More](https://relay.dev/docs/guides/relay-resolvers/introduction/).
+**Relay Resolver**: [Learn More](https://relay.dev/docs/guides/relay-resolvers/introduction/)