commandkit/docs/roadmap/reporting.md

# Output policy and invocation reporting

Status: initial planning. Message categories, the quiet/default/verbose output
policy, and uniform treatment of help and version are selected. A debug mode
extends the proposed hierarchy. Consumer API, flag details, and delivery
mechanics remain open. Implementation has not started.

## Purpose

Provide consistent handling of `--quiet`, `--verbose`, and the proposed
`--debug` mode across application commands and optional integrations. Reduce
repeated output classification, diagnostic presentation, and delivery bookkeeping
where CommandKit can provide a meaningful benefit.

Ordinary Go writers and formatting functions already make application output
straightforward. Design reporting conveniences around the shared output policy
and invocation lifecycle. Applications continue to own their report content,
domain behavior, and operation outcomes.

## Current baseline

[`Streams` and `Invocation`](../../identity.go) expose caller-selected output
and diagnostic writers. [`Outcome` and `Diagnostic`](../../outcome.go) carry
operation causes, diagnostic writers, and delivery state. Handlers can return
`Failure(err)` or attach diagnostics to an outcome for presentation after the
handler returns. `MessageDiagnostic` currently writes the supplied message with
a newline; severity does not add a label automatically.

CommandKit coordinates final diagnostic delivery and retains delivery failures
separately from the operation cause. Custom handlers can also write directly to
the supplied streams and retain responsibility for their output. The existing
outcome and channel ownership decisions are recorded in
[ADR 0005](../adr/0005-invocation-outcomes.md).

Integration adapters already translate upstream diagnostic records into
CommandKit diagnostics while preserving native rendering and source context.
Some adapters wrap multiple records in one diagnostic writer and classify the
batch by its highest severity. This matters when designing selective visibility.

There is currently no shared verbosity policy or invocation reporter API.

## Selected output policy

Distinguish substantive application output from diagnostic message categories:

- **Substantive output (Normal):** The requested report or command result.
- **Error:** The invocation failed and will return a non-zero status code.
- **Warning:** Something went wrong or deserves attention, but the invocation
  can still succeed. A recovered problem is a warning.
- **Info:** Progress or useful explanation, including completion messages.
- **Debug:** Troubleshooting detail, including intermediate decisions and
  execution-path information.

Quiet, ordinary, and verbose presentation follow the selected policy. The
proposed debug mode adds troubleshooting detail to verbose output:

| Output category | `--quiet` | No flag | `--verbose` | `--debug` (proposed) |
| --- | --- | --- | --- | --- |
| Substantive application output | Suppressed | Shown | Shown | Shown |
| Error | Shown | Shown | Shown | Shown |
| Warning | Suppressed | Suppressed | Shown | Shown |
| Info | Suppressed | Suppressed | Shown | Shown |
| Debug | Suppressed | Suppressed | Suppressed | Shown |

Info belongs in verbose mode; debug includes verbose messages. Normal output
remains a substantive result category, separate from diagnostic severity.
The category of a message determines its visibility; stream destination alone
cannot distinguish a warning from an error.

Error presentation is tied to invocation failure. Prefer deriving error
diagnostics from a failed outcome, which may carry detailed explanations. Avoid
an unrestricted `Error(...)` reporting method that permits an error message
followed by a successful outcome. The application still controls process exit
under the existing outcome contract; the returned outcome must consistently
represent the failure and its non-zero status.

Apply the same policy to help and version. There are no command-specific
exceptions for successful output:

```text
app help --quiet       # succeeds silently
app version --quiet    # succeeds silently
```

Usage and operational failures still report their errors in quiet mode.
The feature must distinguish successful output suppression from failure
diagnostic delivery.

## Tentative direction

### Flag and invocation behavior

Model quiet, ordinary, verbose, and debug as mutually exclusive presentation
modes. The proposed rule when multiple mode flags occur is last occurrence wins,
consistent with existing repetition conventions. Exact boolean forms, resets,
short spellings, placement, and collision handling remain to be specified.

Keep verbosity a presentation choice: a quiet invocation still performs its
requested operation and returns the ordinary outcome. Apply the policy through
CommandKit-managed reporting and streams. Output written directly to process
streams or external destinations remains application-owned.

### Streaming and failure diagnostics

The proposed approach applies visibility when output is emitted. A verbose or
debug run may show progress before subsequently failing, and an ordinary run may
write part of its substantive output before failing. Previously written bytes cannot
be withdrawn. Whole-run buffering solely to make failed runs contain only error
output is not part of the proposed direction.

Keep errors understandable in every mode, including source locations and
related explanatory context. Unrelated warnings and informational messages
remain subject to the selected mode. Retain suppressed diagnostics for
programmatic inspection rather than equating suppression with loss of evidence.
The exact representation of retained and delivered diagnostics remains open.

### Consumer reporting API

An invocation-scoped facility could classify messages, coordinate immediate and
end-of-handler presentation, and retain delivery failures. Earlier illustrative
API shapes included `inv.Reporter()`, `Info`, `Warn`, `Diagnostic`, and an
`AtEnd()` view. These names and shapes are exploratory, not selected contracts.
Reassess the necessary API around the output modes and expanded message
categories before adopting them. Debug messages need a corresponding
classification; its exact API remains open.

Continue to support standard `io.Writer` usage for report bodies and native
report writers. Reuse existing diagnostic and outcome concepts where practical.
Any reporting facility should coordinate with returned `Outcome.Diagnostics`
and operation causes so already-presented messages are not repeated.

Whether reporting methods return write errors, retain them for finalization,
or expose an explicit delivery-error accessor remains open. The API must enforce
the selected relationship between Error diagnostics and failed outcomes,
including diagnostics supplied through generic or existing entry points.

### Upstream diagnostic ownership

ConfigKit and PromptKit remain authoritative for their diagnostic semantics,
severity, source context, and disclosure rules. Integration adapters expose
those capabilities through the shared CommandKit presentation policy.

Support consistent reporting of ConfigKit errors and warnings as its adopted
public API evolves. This roadmap does not assume that a future warning API
already exists or prescribe its upstream shape. Preserve useful native
diagnostic detail and supported error identity, and coordinate returned errors
with diagnostics that already explain them.

Debug output follows the same upstream disclosure and safe-rendering contracts.
Enabling debug does not authorize secret disclosure or bypass owning-library
rules.

## Work needed

1. Settle the open decisions with examples covering ordinary application output,
   immediate and deferred diagnostics, failure after partial output, help and
   version, and integration diagnostics in every mode.
2. Review current diagnostic batching, parsing, help, outcome presentation, and
   writer ownership to identify the smallest shared changes. Include invocation
   failures that occur before a handler receives its `Invocation`.
3. Specify the public API and flag contracts, including interactions with command
   and flag aliases. Assess existing flag collisions and compatibility impact.
4. Implement the selected behavior across core and the integrations. Preserve
   upstream rendering and semantics while applying the chosen visibility policy.
5. Verify classification, flag selection, suppression, retained diagnostics,
   ordering, duplicate prevention, Error/non-zero-outcome consistency, debug
   visibility, and write-failure handling with focused behavioral tests and
   maintained consumer examples.
6. Update GoDoc, the CLI reference, consumer guidance, and release documentation
   when implemented. Review whether any resulting architectural change needs an
   ADR; exact reporting APIs and flag syntax remain API/CLI contracts.

## Open Decisions

### OD-1: Flag grammar and scope

How are quiet, verbose, and debug selected, repeated, combined, or explicitly
reset? Are short spellings built in? Where may the flags appear, including on help
requests? How are canonical and alias spelling collisions handled, and how is
the mode determined for invocations that fail during routing or parsing?

### OD-2: Consumer API and output classification

What is the smallest API for substantive output, debug and informational
messages, warnings, and failure diagnostics? How do direct writes through
`Invocation.Streams` interact with it? How can helpers report through the same
invocation? Is a dedicated immediate/deferred reporter needed, and how does it compose with existing
outcome diagnostics?

### OD-3: Failure presentation and diagnostic retention

How does the API enforce that Error diagnostics accompany a failed invocation
with a non-zero status, including application domain outcomes? How should
inconsistent caller-supplied combinations be handled through existing diagnostic
and outcome APIs? How are recovered upstream problems represented as warnings
while preserving their native context?
Which contextual records belong to an error explanation? How are mixed upstream
diagnostic batches filtered while preserving useful native rendering? What is
retained when presentation is suppressed, and how is duplicate presentation
prevented without hiding unrelated failures?

### OD-4: Delivery lifecycle and quiet execution

How are immediate and deferred messages ordered and finalized, including when
the operation fails? How do callers observe and react to write failures? What
delivery state represents intentional suppression? Does quiet mode discard
rendered bytes or skip report rendering, and how does that choice preserve
operation semantics and failure detection? Which streaming behavior becomes
part of the public contract?