Replace a step — pip_replace • pipeflow

Replaces a step's function while keeping it in the same position in the pipeline. Downstream steps are automatically marked as outdated and will re-run on the next pip_run().

Usage

pip_replace(x, step, fun, tags = character(0), params = list(), exec = "auto")

Arguments

x

A pipeflow pipeline or view object.

step

Unique step name.

fun

Function to execute for the step. Each function parameter must have a default value. Default values that are simple constants are resolved immediately. Default values that are formulas like ~other_step are treated as dependencies to those steps and resolved to the respective output values at runtime once the step is executed.

tags

Optional character vector of tags belonging to the step. Can also be adjusted later using [pip_tag()].

params

Optional named list of parameter values, which will be merged with the defaults of fun (if overlapping names, the default values in fun take precedence). There are two use cases for params:

Provide param values programmatically when adding steps at runtime
Provide extra param values to "mark" dependencies that are defined in pipelines nested in a step, which ensures that the step (and with that the pipeline in the step) is re-executed when one of the respective param values change.

exec

Execution mode for this step. One of "auto", "split", "reduce" or "plain". Using execution mode exec = split, the output of the step is marked as partitioned output. In this mode, any step that depends on the split step (directly or indirectly) will have its output automatically mapped partition-wise during step execution. The reduce mode expects partitioned input and passes it through without mapping, while plain mode only accepts non-partitioned input and always intends to execute a single call. In summary:

auto: map if partitioned input appears, otherwise single call
split: single call, then mark output as partitioned
reduce: single call, but only valid with partitioned input
plain: single call, only valid with non-partitioned input

Value

The updated pipeline, invisibly.

Examples

p <- pip_new() |>
    pip_add("load", \(n = 5) seq_len(n)) |>
    pip_add("double", \(x = ~load) x * 2)
pip_run(p)
#> info [2026-10-02 18:37:07.511 UTC]: Starting run of pipeflow 'pipe'
#> info [2026-10-02 18:37:07.511 UTC]: Step 1/2 load
#> info [2026-10-02 18:37:07.512 UTC]: Step 2/2 double
#> info [2026-10-02 18:37:07.513 UTC]: Finished run of pipeflow 'pipe'
p
#> <pipeflow> pipe (2 steps)
#> -------------------------
#>      step params depends state            out
#> 1:   load      n          done      1,2,3,4,5
#> 2: double      x    load  done  2, 4, 6, 8,10
#> -------------------------
#> <ready> last run: 2026-10-02 20:37:07

# Replace "load" — downstream steps are automatically marked "outdated"
pip_replace(p, "load", \(n = 3) seq_len(n))
p
#> <pipeflow> pipe (2 steps)
#> -------------------------
#>      step params depends    state            out
#> 1:   load      n              new         [NULL]
#> 2: double      x    load outdated  2, 4, 6, 8,10
#> -------------------------
#> <ready> last run: 2026-10-02 20:37:07

# Re-run to bring everything up to date
pip_run(p)
#> info [2026-10-02 18:37:07.518 UTC]: Starting run of pipeflow 'pipe'
#> info [2026-10-02 18:37:07.518 UTC]: Step 1/2 load
#> info [2026-10-02 18:37:07.518 UTC]: Step 2/2 double
#> info [2026-10-02 18:37:07.519 UTC]: Finished run of pipeflow 'pipe'
p
#> <pipeflow> pipe (2 steps)
#> -------------------------
#>      step params depends state   out
#> 1:   load      n          done 1,2,3
#> 2: double      x    load  done 2,4,6
#> -------------------------
#> <ready> last run: 2026-10-02 20:37:07

# If a view is passed, the step must be part of the view
v <- pip_view(p, step = "double")
pip_replace(v, "double", \(x = ~load) x * 3)
p[["state"]]                                # "double" is "new" again
#>   load double 
#> "done"  "new" 

try(pip_replace(v, "load", \(n = 2) seq_len(n)))
#> Error in pip_replace(v, "load", function(n = 2) seq_len(n)) : 
#>   step 'load' is not part of the view