@rushstack/operation-graph/lib/calculateCriticalPath.js

Library for managing and executing operations in a directed acyclic graph.

"use strict";
// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
// See LICENSE in the project root for license information.
Object.defineProperty(exports, "__esModule", { value: true });
exports.calculateCriticalPathLength = exports.calculateShortestPath = exports.calculateCriticalPathLengths = void 0;
/**
 * For every operation in the input, computes the length of the longest chain of operations that depend on it.
 * This value is stored as `operation.criticalPathLength`.
 */
function calculateCriticalPathLengths(operations) {
    // Clone the set of operations as an array, so that we can sort it.
    const queue = Array.from(operations);
    // Create a collection for detecting visited nodes
    const cycleDetectorStack = new Set();
    for (const operation of queue) {
        calculateCriticalPathLength(operation, cycleDetectorStack);
    }
    return queue;
}
exports.calculateCriticalPathLengths = calculateCriticalPathLengths;
/**
 * Calculates the shortest path from `startOperation` to `endOperation`.
 * Used when printing out circular dependencies.
 */
function calculateShortestPath(startOperation, endOperation) {
    // Map of each operation to the most optimal parent
    const parents = new Map([[endOperation, undefined]]);
    let finalParent;
    // Run a breadth-first search to find the shortest path between the start and end operations
    outer: for (const [operation] of parents) {
        for (const consumer of operation.consumers) {
            // Since this is a breadth-first traversal, the first encountered path to a given node
            // will be tied for shortest, so only the first encountered path needs to be tracked
            if (!parents.has(consumer)) {
                parents.set(consumer, operation);
            }
            if (consumer === startOperation) {
                finalParent = operation;
                break outer;
            }
        }
    }
    if (!finalParent) {
        throw new Error(`Could not find a path from "${startOperation.name}" to "${endOperation.name}"`);
    }
    // Walk back up the path from the end operation to the start operation
    let currentOperation = finalParent;
    const path = [startOperation];
    while (currentOperation !== undefined) {
        path.push(currentOperation);
        currentOperation = parents.get(currentOperation);
    }
    return path;
}
exports.calculateShortestPath = calculateShortestPath;
/**
 * Perform a depth-first search to find critical path length to the provided operation.
 * Cycle detection comes at minimal additional cost.
 */
function calculateCriticalPathLength(operation, dependencyChain) {
    if (dependencyChain.has(operation)) {
        // Ensure we have the shortest path to the cycle
        const shortestPath = calculateShortestPath(operation, operation);
        throw new Error('A cyclic dependency was encountered:\n  ' +
            shortestPath.map((visitedTask) => visitedTask.name).join('\n  -> '));
    }
    let { criticalPathLength } = operation;
    if (criticalPathLength !== undefined) {
        // This has been visited already
        return criticalPathLength;
    }
    criticalPathLength = 0;
    if (operation.consumers.size) {
        dependencyChain.add(operation);
        for (const consumer of operation.consumers) {
            criticalPathLength = Math.max(criticalPathLength, calculateCriticalPathLength(consumer, dependencyChain));
        }
        dependencyChain.delete(operation);
    }
    // Include the contribution from the current operation
    criticalPathLength += operation.weight ?? 1;
    // Record result
    operation.criticalPathLength = criticalPathLength;
    // Directly writing operations to an output collection here would yield a topological sorted set
    // However, we want a bit more fine-tuning of the output than just the raw topology
    return criticalPathLength;
}
exports.calculateCriticalPathLength = calculateCriticalPathLength;
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