TypeError: Cannot read property 'slice' of undefined

[victor-homyakov]

Sometimes I see an error when using this package

(node:67818) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'slice' of undefined
    at /project/node_modules/dependencies-tree-builder/src/scoupe_factory.js:61:40
    at Array.filter (<anonymous>)
    at /project/node_modules/dependencies-tree-builder/src/scoupe_factory.js:54:44
    at Array.forEach (<anonymous>)
    at /project/node_modules/dependencies-tree-builder/src/scoupe_factory.js:48:19
    at Array.forEach (<anonymous>)
    at ScoupeFactory._dedupeUsages (/project/node_modules/dependencies-tree-builder/src/scoupe_factory.js:44:27)
    at ScoupeFactory.create (/project/node_modules/dependencies-tree-builder/src/scoupe_factory.js:117:10)
    at module.exports (/project/node_modules/dependencies-tree-builder/src/index.js:45:32)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)

[victor-homyakov]

More info.

At the line

const { usages, tunable } = data;

(https://github.com/itwillwork/dependencies-tree-builder/blob/master/src/scoupe_factory.js#L49)

object data has the following value:

{
  usages: [ undefined, undefined, undefined, undefined, undefined ],
  version: undefined,
  name: undefined,
  tunable: true
}

[victor-homyakov]

Monkey-patching helps to see at least some results

        const { usages, tunable } = data;

        const carriers = {};

        const sortedUsages = [...usages].sort(byLengthAsc);
-       const dedupedUsages = sortedUsages.filter(usage => {
+       const dedupedUsages = sortedUsages.filter((usage = []) => {
          let startUsagePath = 1;

          if (hasOnlyOneVersion || tunable) {
            startUsagePath = 0;
          }

          const effectiveUsage = usage.slice(startUsagePath);

[victor-homyakov]

The problem is in package cache. If cache already exists and has any (even outdated) information about some library, then this information is used.

Steps to reproduce:

1. Create package.json with some dependency, say [email protected] (1.0.0 is the latest version)
2. Run dependencies tree builder
3. It creates node_modules/dependencies-tree-builder/.packages.cache.json where are listed all currently known versions of dependency X (e.g. 0.9.0, 1.0.0)
4. Release the new version of X (e.g. [email protected]), and update dependency in package.json ([email protected] -> [email protected])
5. Run dependencies tree builder again. Now it finds already existing cache, the cache knows about the library X, but the cache does not contain any information about [email protected]!

[victor-homyakov]

Right now the easiest way to avoid this error is to delete node_modules/dependencies-tree-builder/.packages.cache.json just before running dependencies tree builder or use corresponding option

const buildTreeAsync = require('dependencies-tree-builder');
const {scoupe} = await buildTreeAsync(packageJson, {useCache: false});