pnpm-flawed-topo

Replication scenario for pnpm flawed topological sort.

We have the following dependency graph: a -> b -> c

Legend: -> = depends on

Replicate bug

Run in monorepo root the following command:

pnpm run \
    --filter a \
    --filter c \
    build

You will get the following output:

Scope: 2 of 4 workspace projects
a build$ echo 'Building a ...'
│ Building a ...
└─ Done in 21ms
c build$ echo 'Building c ...'
│ Building c ...
└─ Done in 22ms

As you can observe, a is built before or at best concurrently with c, although c is a transitive dependency of a.

Workaround - performance penalty

If we include all dependents of c in the filter then the topological sort is correct, but we are building more workspaces than wanted:

pnpm run \
    --filter a \
    --filter ...c \
    build

Now we get the following output:

Scope: 3 of 4 workspace projects
c build$ echo 'Building c ...'
│ Building c ...
└─ Done in 11ms
b build$ echo 'Building b ...'
│ Building b ...
└─ Done in 7ms
a build$ echo 'Building a ...'
│ Building a ...
└─ Done in 6ms