81 lines
2.4 KiB
Plaintext
81 lines
2.4 KiB
Plaintext
// @flow strict
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import { GraphQLError } from '../../error/GraphQLError';
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import { type ASTVisitor } from '../../language/visitor';
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import { type FragmentDefinitionNode } from '../../language/ast';
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import { type ASTValidationContext } from '../ValidationContext';
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export function cycleErrorMessage(
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fragName: string,
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spreadNames: $ReadOnlyArray<string>,
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): string {
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const via = spreadNames.length ? ' via ' + spreadNames.join(', ') : '';
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return `Cannot spread fragment "${fragName}" within itself${via}.`;
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}
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export function NoFragmentCycles(context: ASTValidationContext): ASTVisitor {
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// Tracks already visited fragments to maintain O(N) and to ensure that cycles
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// are not redundantly reported.
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const visitedFrags = Object.create(null);
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// Array of AST nodes used to produce meaningful errors
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const spreadPath = [];
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// Position in the spread path
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const spreadPathIndexByName = Object.create(null);
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return {
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OperationDefinition: () => false,
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FragmentDefinition(node) {
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detectCycleRecursive(node);
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return false;
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},
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};
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// This does a straight-forward DFS to find cycles.
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// It does not terminate when a cycle was found but continues to explore
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// the graph to find all possible cycles.
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function detectCycleRecursive(fragment: FragmentDefinitionNode) {
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if (visitedFrags[fragment.name.value]) {
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return;
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}
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const fragmentName = fragment.name.value;
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visitedFrags[fragmentName] = true;
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const spreadNodes = context.getFragmentSpreads(fragment.selectionSet);
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if (spreadNodes.length === 0) {
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return;
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}
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spreadPathIndexByName[fragmentName] = spreadPath.length;
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for (const spreadNode of spreadNodes) {
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const spreadName = spreadNode.name.value;
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const cycleIndex = spreadPathIndexByName[spreadName];
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spreadPath.push(spreadNode);
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if (cycleIndex === undefined) {
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const spreadFragment = context.getFragment(spreadName);
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if (spreadFragment) {
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detectCycleRecursive(spreadFragment);
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}
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} else {
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const cyclePath = spreadPath.slice(cycleIndex);
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const fragmentNames = cyclePath.slice(0, -1).map(s => s.name.value);
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context.reportError(
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new GraphQLError(
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cycleErrorMessage(spreadName, fragmentNames),
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cyclePath,
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),
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);
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}
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spreadPath.pop();
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}
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spreadPathIndexByName[fragmentName] = undefined;
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}
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}
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