Does NPM try to install same dependent package multiple times or only once?

user_13380017 0
Viewed 308

Would like to understand, how npm handles installation of duplicate packages with same version.

  1. Does it ignore, if the same package - same version installed already?
  2. Does it install/overwrite again the same package?

For eg:

  1. Package A is dependent on package B and package C.
  2. Where Packages B and C are dependent on common package D version 1.0

so while running npm install will it try to install package D twice or only once and will ignore second occurrence as its already present in node_modules?

package.json npm npm-install
1 Answers

The NPM install algorithm states dependencies will be added as close to the top as is possible without breaking any other modules.

In your case, package B and C both depend on D@1.0. Since there is no possible conflict between the two dependencies, package D will be installed once at the top level.

For a rough representation, here is the original dependency tree you have imagined.

+ package A
+-- B
   -- D@1.0
+-- C
   -- D@1.0

Package A installs dep B and dep C at the same top level. Since there are no other conflicting versions of dep D in the tree, dep D also gets added to the top level for both dep B and dep C to use.

+ package A
+-- B
+-- C
+-- D@1.0
user_122860150
Related