I want to install a local package (let's say foo.jl) in the default environment because I don't want to activate the package environment (Pkg.activate("\path\to\foo.jl")) every time.
However, when I try to install the package by Pkg.add(path=\path\to\foo\), it seems that the project.toml of the foo.jl was not followed. Specifically, foo.jl requires "JuMP=1.5.0" in the project.toml compatibility module, but "JuMP=1.9.0" was installed and was added to the project.toml of the default environment.
Could anyone please explain how the process works? I know I can use "instantiate" to reproduce the environment, but it creates a project environment and installs the package instead of installing the package in the default environment.
Julia uses semantic versioning for package compatibility.
If you write JuMP="1.5.0" the acceptable version include [1.5.0 - 2.0.0) (note that the range is open on the right side). Since 1.9.0 is currently the latest version, it gets installed and this is the correct expected behavior.
Most likely what you wanted is:
JuMP="=1.5.0"
such line would ensure that exactly the version 1.5.0 gets installed.
The way you are adding the packages seems to be correct.
For more details on semantic versioning see: https://pkgdocs.julialang.org/v1/compatibility/