[HelpDot] detect infinite redirect cycles in redirects.csv #40434
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| Original file line number | Diff line number | Diff line change | ||||||||
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| @@ -0,0 +1,64 @@ | ||||||||||
| import {parse} from 'csv-parse'; | ||||||||||
| import fs from 'fs'; | ||||||||||
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| const parser = parse(); | ||||||||||
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| const adjacencyList: Record<string, string[]> = {}; | ||||||||||
| const visited: Map<string, boolean> = new Map<string, boolean>(); | ||||||||||
| const backEdges: Map<string, boolean> = new Map<string, boolean>(); | ||||||||||
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| function addEdge(source: string, target: string) { | ||||||||||
| if (!adjacencyList[source]) { | ||||||||||
| adjacencyList[source] = []; | ||||||||||
| } | ||||||||||
| adjacencyList[source].push(target); | ||||||||||
| } | ||||||||||
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| function isCyclic(currentNode: string): boolean { | ||||||||||
| visited.set(currentNode, true); | ||||||||||
| backEdges.set(currentNode, true); | ||||||||||
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| // Do a depth first search for all the neighbours. If a node is found in backedge, a cycle is detected. | ||||||||||
| const neighbours = adjacencyList[currentNode]; | ||||||||||
| if (neighbours) { | ||||||||||
| for (const node of neighbours) { | ||||||||||
| if (!visited.has(node)) { | ||||||||||
| if (isCyclic(node)) { | ||||||||||
| return true; | ||||||||||
| } | ||||||||||
| } else if (backEdges.has(node)) { | ||||||||||
| return true; | ||||||||||
| } | ||||||||||
| } | ||||||||||
| } | ||||||||||
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| backEdges.delete(currentNode); | ||||||||||
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| return false; | ||||||||||
| } | ||||||||||
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| function detectCycle(): boolean { | ||||||||||
| for (const [node] of Object.entries(adjacencyList)) { | ||||||||||
| if (!visited.has(node)) { | ||||||||||
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There was a problem hiding this comment. linter does not like There was a problem hiding this comment. I don't like that lint rule tbh, but this is fine for now |
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| if (isCyclic(node)) { | ||||||||||
| const cycle = Array.from(backEdges.keys()); | ||||||||||
| console.log(`Infinite redirect found in the cycle: ${cycle.join(' -> ')} -> ${node}`); | ||||||||||
| return true; | ||||||||||
| } | ||||||||||
| } | ||||||||||
| } | ||||||||||
| return false; | ||||||||||
| } | ||||||||||
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| fs.createReadStream(`${process.cwd()}/docs/redirects.csv`) | ||||||||||
| .pipe(parser) | ||||||||||
| .on('data', (row) => { | ||||||||||
| // Create a directed graph of sourceURL -> targetURL | ||||||||||
| addEdge(row[0], row[1]); | ||||||||||
| }) | ||||||||||
| .on('end', () => { | ||||||||||
| if (detectCycle()) { | ||||||||||
| process.exit(1); | ||||||||||
| } | ||||||||||
| process.exit(0); | ||||||||||
| }); | ||||||||||
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Looks like you could safely remove this if statement
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No, there will be nodes that have no neighbours because this is a directed graph.
eg:
Graph will look like this
urlA -> urlBurlBhas no neighbours that we can go to. So we'll try to iterate over undefined in next line