refactor(graphqlsp): Add declaration helpers to replace language services (#351)

Co-authored-by: Jovi De Croock <decroockjovi@gmail.com>

Author: kitten

.changeset/puny-ghosts-clap.md

@@ -0,0 +1,5 @@
+---
+'@0no-co/graphqlsp': minor
+---
+
+Add new value declaration helpers to replace built-in services and to traverse TypeScript type checked AST exhaustively and efficiently.

packages/graphqlsp/src/ast/declaration.ts

@@ -0,0 +1,353 @@
+import { ts } from '../ts';
+
+export type ValueDeclaration =
+  | ts.BinaryExpression
+  | ts.ArrowFunction
+  | ts.BindingElement
+  | ts.ClassDeclaration
+  | ts.ClassExpression
+  | ts.ClassStaticBlockDeclaration
+  | ts.ConstructorDeclaration
+  | ts.EnumDeclaration
+  | ts.EnumMember
+  | ts.ExportSpecifier
+  | ts.FunctionDeclaration
+  | ts.FunctionExpression
+  | ts.GetAccessorDeclaration
+  | ts.JsxAttribute
+  | ts.MethodDeclaration
+  | ts.ModuleDeclaration
+  | ts.ParameterDeclaration
+  | ts.PropertyAssignment
+  | ts.PropertyDeclaration
+  | ts.SetAccessorDeclaration
+  | ts.ShorthandPropertyAssignment
+  | ts.VariableDeclaration;
+
+export type ValueOfDeclaration =
+  | ts.ClassExpression
+  | ts.ClassDeclaration
+  | ts.ArrowFunction
+  | ts.ClassStaticBlockDeclaration
+  | ts.ConstructorDeclaration
+  | ts.EnumDeclaration
+  | ts.FunctionDeclaration
+  | ts.GetAccessorDeclaration
+  | ts.SetAccessorDeclaration
+  | ts.MethodDeclaration
+  | ts.Expression;
+
+/** Checks if a node is a `ts.Declaration` and a value.
+ * @remarks
+ * This checks if a given node is a value declaration only,
+ * excluding import/export specifiers, type declarations, and
+ * ambient declarations.
+ * All declarations that aren't JS(x) nodes will be discarded.
+ * This is based on `ts.isDeclarationKind`.
+ */
+export function isValueDeclaration(node: ts.Node): node is ValueDeclaration {
+  switch (node.kind) {
+    case ts.SyntaxKind.BinaryExpression:
+    case ts.SyntaxKind.ArrowFunction:
+    case ts.SyntaxKind.BindingElement:
+    case ts.SyntaxKind.ClassDeclaration:
+    case ts.SyntaxKind.ClassExpression:
+    case ts.SyntaxKind.ClassStaticBlockDeclaration:
+    case ts.SyntaxKind.Constructor:
+    case ts.SyntaxKind.EnumDeclaration:
+    case ts.SyntaxKind.EnumMember:
+    case ts.SyntaxKind.FunctionDeclaration:
+    case ts.SyntaxKind.FunctionExpression:
+    case ts.SyntaxKind.GetAccessor:
+    case ts.SyntaxKind.JsxAttribute:
+    case ts.SyntaxKind.MethodDeclaration:
+    case ts.SyntaxKind.Parameter:
+    case ts.SyntaxKind.PropertyAssignment:
+    case ts.SyntaxKind.PropertyDeclaration:
+    case ts.SyntaxKind.SetAccessor:
+    case ts.SyntaxKind.ShorthandPropertyAssignment:
+    case ts.SyntaxKind.VariableDeclaration:
+      return true;
+    default:
+      return false;
+  }
+}
+
+/** Returns true if operator assigns a value unchanged */
+function isAssignmentOperator(token: ts.BinaryOperatorToken): boolean {
+  switch (token.kind) {
+    case ts.SyntaxKind.EqualsToken:
+    case ts.SyntaxKind.BarBarEqualsToken:
+    case ts.SyntaxKind.AmpersandAmpersandEqualsToken:
+    case ts.SyntaxKind.QuestionQuestionEqualsToken:
+      return true;
+    default:
+      return false;
+  }
+}
+
+/** Evaluates to the declaration's value initializer or itself if it declares a value */
+export function getValueOfValueDeclaration(
+  node: ValueDeclaration
+): ValueOfDeclaration | undefined {
+  switch (node.kind) {
+    case ts.SyntaxKind.ClassExpression:
+    case ts.SyntaxKind.ClassDeclaration:
+    case ts.SyntaxKind.ArrowFunction:
+    case ts.SyntaxKind.ClassStaticBlockDeclaration:
+    case ts.SyntaxKind.Constructor:
+    case ts.SyntaxKind.EnumDeclaration:
+    case ts.SyntaxKind.FunctionDeclaration:
+    case ts.SyntaxKind.FunctionExpression:
+    case ts.SyntaxKind.GetAccessor:
+    case ts.SyntaxKind.SetAccessor:
+    case ts.SyntaxKind.MethodDeclaration:
+      return node;
+    case ts.SyntaxKind.BindingElement:
+    case ts.SyntaxKind.EnumMember:
+    case ts.SyntaxKind.JsxAttribute:
+    case ts.SyntaxKind.Parameter:
+    case ts.SyntaxKind.PropertyAssignment:
+    case ts.SyntaxKind.PropertyDeclaration:
+    case ts.SyntaxKind.VariableDeclaration:
+      return node.initializer;
+    case ts.SyntaxKind.BinaryExpression:
+      return isAssignmentOperator(node.operatorToken) ? node.right : undefined;
+    case ts.SyntaxKind.ShorthandPropertyAssignment:
+      return node.objectAssignmentInitializer;
+    default:
+      return undefined;
+  }
+}
+
+// See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/utilities.ts#L652-L654
+function climbPastPropertyOrElementAccess(node: ts.Node): ts.Node {
+  if (
+    node.parent &&
+    ts.isPropertyAccessExpression(node.parent) &&
+    node.parent.name === node
+  ) {
+    return node.parent;
+  } else if (
+    node.parent &&
+    ts.isElementAccessExpression(node.parent) &&
+    node.parent.argumentExpression === node
+  ) {
+    return node.parent;
+  } else {
+    return node;
+  }
+}
+
+// See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/utilities.ts#L602-L605
+function isNewExpressionTarget(node: ts.Node): node is ts.NewExpression {
+  const target = climbPastPropertyOrElementAccess(node).parent;
+  return ts.isNewExpression(target) && target.expression === node;
+}
+
+// See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/utilities.ts#L607-L610
+function isCallOrNewExpressionTarget(
+  node: ts.Node
+): node is ts.CallExpression | ts.NewExpression {
+  const target = climbPastPropertyOrElementAccess(node).parent;
+  return ts.isCallOrNewExpression(target) && target.expression === node;
+}
+
+// See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/utilities.ts#L716-L719
+function isNameOfFunctionDeclaration(node: ts.Node): boolean {
+  return (
+    ts.isIdentifier(node) &&
+    node.parent &&
+    ts.isFunctionLike(node.parent) &&
+    node.parent.name === node
+  );
+}
+
+// See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/utilities.ts#L2441-L2447
+function getNameFromPropertyName(name: ts.PropertyName): string | undefined {
+  if (ts.isComputedPropertyName(name)) {
+    return ts.isStringLiteralLike(name.expression) ||
+      ts.isNumericLiteral(name.expression)
+      ? name.expression.text
+      : undefined;
+  } else if (ts.isPrivateIdentifier(name) || ts.isMemberName(name)) {
+    return ts.idText(name);
+  } else {
+    return name.text;
+  }
+}
+
+/** Resolves the declaration of an identifier.
+ * @remarks
+ * This returns the declaration node first found for an identifier by resolving an identifier's
+ * symbol via the type checker.
+ * @privateRemarks
+ * This mirrors the implementation of `getDefinitionAtPosition` in TS' language service. However,
+ * it removes all cases that aren't applicable to identifiers and removes the intermediary positional
+ * data structure, instead returning raw AST nodes.
+ */
+export function getDeclarationOfIdentifier(
+  node: ts.Identifier,
+  checker: ts.TypeChecker
+): ValueDeclaration | undefined {
+  // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L523-L540
+  let symbol = checker.getSymbolAtLocation(node);
+  if (
+    symbol?.declarations?.[0] &&
+    symbol.flags & ts.SymbolFlags.Alias &&
+    (node.parent === symbol?.declarations?.[0] ||
+      !ts.isNamespaceImport(symbol.declarations[0]))
+  ) {
+    // Resolve alias symbols, excluding self-referential symbols
+    const aliased = checker.getAliasedSymbol(symbol);
+    if (aliased.declarations) symbol = aliased;
+  }
+
+  if (symbol && ts.isShorthandPropertyAssignment(node.parent)) {
+    // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L248-L257
+    // Resolve shorthand property assignments
+    const shorthandSymbol = checker.getShorthandAssignmentValueSymbol(
+      symbol.valueDeclaration
+    );
+    if (shorthandSymbol) symbol = shorthandSymbol;
+  } else if (
+    ts.isBindingElement(node.parent) &&
+    ts.isObjectBindingPattern(node.parent.parent) &&
+    node === (node.parent.propertyName || node.parent.name)
+  ) {
+    // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L259-L280
+    // Resolve symbol of property in shorthand assignments
+    const name = getNameFromPropertyName(node);
+    const prop = name
+      ? checker.getTypeAtLocation(node.parent.parent).getProperty(name)
+      : undefined;
+    if (prop) symbol = prop;
+  } else if (
+    ts.isObjectLiteralElement(node.parent) &&
+    (ts.isObjectLiteralExpression(node.parent.parent) ||
+      ts.isJsxAttributes(node.parent.parent)) &&
+    node.parent.name === node
+  ) {
+    // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L298-L316
+    // Resolve symbol of property in object literal destructre expressions
+    const name = getNameFromPropertyName(node);
+    const prop = name
+      ? checker.getContextualType(node.parent.parent)?.getProperty(name)
+      : undefined;
+    if (prop) symbol = prop;
+  }
+
+  if (symbol && symbol.declarations?.length) {
+    if (
+      symbol.flags & ts.SymbolFlags.Class &&
+      !(symbol.flags & (ts.SymbolFlags.Function | ts.SymbolFlags.Variable)) &&
+      isNewExpressionTarget(node)
+    ) {
+      // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L603-L610
+      // Resolve first class-like declaration for new expressions
+      for (const declaration of symbol.declarations) {
+        if (ts.isClassLike(declaration)) return declaration;
+      }
+    } else if (
+      isCallOrNewExpressionTarget(node) ||
+      isNameOfFunctionDeclaration(node)
+    ) {
+      // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L612-L616
+      // Resolve first function-like declaration for call expressions or named functions
+      for (const declaration of symbol.declarations) {
+        if (
+          ts.isFunctionLike(declaration) &&
+          !!(declaration as ts.FunctionLikeDeclaration).body &&
+          isValueDeclaration(declaration)
+        ) {
+          return declaration;
+        }
+      }
+    }
+
+    // Account for assignments to property access expressions
+    // This resolves property access expressions to binding element parents
+    if (
+      symbol.valueDeclaration &&
+      ts.isPropertyAccessExpression(symbol.valueDeclaration)
+    ) {
+      const parent = symbol.valueDeclaration.parent;
+      if (
+        parent &&
+        ts.isBinaryExpression(parent) &&
+        parent.left === symbol.valueDeclaration
+      ) {
+        return parent;
+      }
+    }
+
+    if (
+      symbol.valueDeclaration &&
+      isValueDeclaration(symbol.valueDeclaration)
+    ) {
+      // NOTE: We prefer value declarations, since the checker may have already applied conditions
+      // similar to `isValueDeclaration` and selected it beforehand
+      // Only use value declarations if they're not type/ambient declarations or imports/exports
+      return symbol.valueDeclaration;
+    }
+
+    // Selecting the first available result, if any
+    // NOTE: We left out `!isExpandoDeclaration` as a condition, since `valueDeclaration` above
+    // should handle some of these cases, and we don't have to care about this subtlety as much for identifiers
+    // See: https://github.com/microsoft/TypeScript/blob/a5eec24/src/services/goToDefinition.ts#L582-L590
+    for (const declaration of symbol.declarations) {
+      // Only use declarations if they're not type/ambient declarations or imports/exports
+      if (isValueDeclaration(declaration)) return declaration;
+    }
+  }
+
+  return undefined;
+}
+
+/** Loops {@link getDeclarationOfIdentifier} until a value of the identifier is found */
+export function getValueOfIdentifier(
+  node: ts.Identifier,
+  checker: ts.TypeChecker
+): ValueOfDeclaration | undefined {
+  while (ts.isIdentifier(node)) {
+    const declaration = getDeclarationOfIdentifier(node, checker);
+    if (!declaration) {
+      return undefined;
+    } else {
+      const value = getValueOfValueDeclaration(declaration);
+      if (value && ts.isIdentifier(value) && value !== node) {
+        // If the resolved value is another identifiers, we continue searching, if the
+        // identifier isn't self-referential
+        node = value;
+      } else {
+        return value;
+      }
+    }
+  }
+}
+
+/** Resolves exressions that might not influence the target identifier */
+export function getIdentifierOfChainExpression(
+  node: ts.Expression
+): ts.Identifier | undefined {
+  let target: ts.Expression | undefined = node;
+  while (target) {
+    if (ts.isPropertyAccessExpression(target)) {
+      target = target.name;
+    } else if (
+      ts.isAsExpression(target) ||
+      ts.isSatisfiesExpression(target) ||
+      ts.isNonNullExpression(target) ||
+      ts.isParenthesizedExpression(target) ||
+      ts.isExpressionWithTypeArguments(target)
+    ) {
+      target = target.expression;
+    } else if (ts.isCommaListExpression(target)) {
+      target = target.elements[target.elements.length - 1];
+    } else if (ts.isIdentifier(target)) {
+      return target;
+    } else {
+      return;
+    }
+  }
+}