# `StatifierBlocks.Core.Placeholder` [🔗](https://github.com/riddler/statifier_blocks/blob/v0.44.1/lib/statifier_blocks/core/placeholder.ex#L1) `core.placeholder`: an in-flow leaf marking a gap the author has left on purpose (ADR-0002's amendment of 2026-08-31, section G10). It compiles to a step that does nothing and it warns. Both halves matter. The step is real, so the chart runs and a preview walks straight through the gap - an author previewing a half-built workflow sees the half they built, which is what makes a marker cheaper to place than a hole. The warning is where the reminder belongs: in the compile, addressed to the author, rather than in the running machine addressed to nobody (ADR-0004's amendment of the same date, D4 and D5). ## Declarations Every callback but four is the default `use StatifierBlocks.BlockType` injects (ADR-0007 decision 1), and that is the point rather than an economy. `io/1` in particular takes ADR-0003 decision 5's permissive default in full - `kinds: [:step]`, `consumes: :unknown`, `produces: :unknown` - which section A3 of that record's amendment states is the honest answer: a gap goes wherever a step goes, and declaring anything narrower would be this package deciding what an author's unwritten step was going to do. The one config field, `note`, is prose and this package never reads it. It exists so a gap can carry the author's own words into the editor's card and into the compile warning. Nothing parses it, nothing routes on it, and an empty one is not a finding: an unexplained gap is still a gap, and refusing one would make the marker more expensive to place than leaving the hole unmarked, which inverts the whole point (G10b). No `icon` is declared. The icon seam treats an entry that names no icon as a nameless entry rather than a missing one and draws no tile at all, and a marker for something not yet written is exactly that case. ## Against `core.drafts` The two types are opposites and shipped together on purpose (G10a). `StatifierBlocks.Core.Drafts` holds work that is **not** in the flow and says nothing about it; a placeholder block **is** in the flow and says something is missing from it. An author moving a fragment off the shelf into the flow is filling a gap; an author who has not built the fragment yet marks the gap instead. ## The word "placeholder" The compiler already uses it: an `StatifierBlocks.Emission` carries `{:child, block_id}` markers that ADR-0004 decision 10's Emit stage splices each child's emission into, and both the code and that record call those **child placeholders**. They are an internal step of one compile, never stored, never rendered and never seen by an author. A placeholder block is the opposite in every one of those respects (G10a-i). # `emit` The smallest thing a step can be: one compound state carrying a single `` reached on entry, so the block completes immediately and the parent's ordinary `done.state` sequencing carries on to the next sibling (D5). There is no ``, no raised event and no data written. A marker that announced itself into the chart would be a marker the author had to remember to remove before the chart was real. # `validate_config` Refuses a `note` that is not a string, and refuses nothing else. An absent `note` and an empty one are both accepted (G10b). --- *Consult [api-reference.md](api-reference.md) for complete listing*