❓ WhyPackage

Explains why the specified package is installed in the project. Equivalent to composer why package/name.

When to use

• 🤔 You see an unfamiliar package in the dependency list and want to know who pulled it in.
• 🧹 Confirm whether other packages still depend on it before removing a package.
• 🐛 Troubleshoot "why a particular version of a transitive dependency was installed".

Signature

func (c *Composer) WhyPackage(packageName string) (string, error)

Parameters

Parameter	Type	Description
packageName	string	Name of the package whose install reason to query

Return value

Value	Type	Description
Output	string	Output of the install reason, listing the dependency chain
Error	error	Returned when an error occurs during the query

Example

package main

import (
    "fmt"
    "log"

    "github.com/scagogogo/composer-skills/pkg/composer"
)

func main() {
    comp, err := composer.New(composer.DefaultOptions())
    if err != nil {
        log.Fatalf("init failed: %v", err)
    }

    output, err := comp.WhyPackage("symfony/polyfill-mbstring")
    if err != nil {
        log.Fatalf("query install reason failed: %v", err)
    }
    fmt.Println("install reason:", output)
}

Advanced

WhyWithOptions

Use this when you need additional options (e.g. --recursive):

func (c *Composer) WhyWithOptions(packageName string, options map[string]string) (string, error)

Reverse question

To find out "why a particular version cannot be installed", use WhyNotPackage; to find out "which packages depend on a package", use ShowReverseDependencies (composer depends).

Difference between why and depends

why answers "why does this package exist" and outputs the dependency chain; depends answers "who depends on it" and outputs reverse dependencies. The two perspectives are complementary.

🔍 Related methods

• WhyNotPackage: explain why a specific version cannot be installed.
• ShowDependencyTree: view the full dependency tree.