schemaui 0.12.4

A Rust library for generating TUI and Web UIs from JSON Schemas for configuration management.
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schemaui turns JSON Schema documents into interactive TUI and Web editors. The terminal path is powered by ratatui, crossterm, and jsonschema; the browser path ships as an embedded SPA behind the same schema → form → validate pipeline.

The library parses rich schemas (nested sections, $ref, arrays, key/value maps, pattern properties…) into a navigable form tree, renders it as a keyboard-first TUI or a browser form, and validates after every edit so users always see the full list of issues before saving.

CLI available: schemaui-cli installs the schemaui binary. Prefer the CLI? Jump to CLI installation and usage.

Surfaces at a Glance

Surface Who uses it How to start
TUI (default CLI mode) Terminal workflows, SSH, scripts schemaui -s schema.json -c config.yaml or schemaui tui …
Web UI Browser editing with live JSON preview schemaui web -s schema.json -c config.yaml
Library API Embed in your Rust app SchemaUI::run (TUI) or schemaui::web::session (Web)

Terminal demo (asciinema above) and Web UI (schema tree + form + live JSON side-by-side):

Feature Highlights

  • Schema fidelity – draft-07 compatible, including $ref, definitions, patternProperties, enums, numeric ranges, and nested objects/arrays.
  • Sections & overlays – top-level properties become root tabs, nested objects are flattened into sections, and complex nodes (composites, key/value collections, array entries) open dedicated overlays with their own validators.
  • Immediate validation – every keystroke can trigger jsonschema::Validator, and all errors (field-scoped + global) are collected and displayed together.
  • Pluggable I/O – io::input ingests JSON/YAML/TOML (feature-gated) while io::output can emit to stdout and/or multiple files in any enabled format.
  • Batteries-included CLI – schemaui-cli offers the same pipeline as the library, including multi-destination output, stdin/inline specs, and aggregated diagnostics.
  • Embedded Web UI – enabling the web feature bundles a browser UI and exposes helpers under schemaui::web::session so host applications can serve the experience without reimplementing the stack.

Config Schema Auto-Detection

When you launch the CLI with --config and omit --schema, schemaui-cli now resolves the schema in this order:

  1. Explicit --schema
  2. A schema declaration embedded in the config document
  3. Fallback inference via schema_from_data_value

Supported declarations:

  • JSON: root $schema
  • TOML: #:schema ./schema.json
  • YAML: # yaml-language-server: $schema=...
  • YAML fallback: # @schema ...

Both local and remote schema references are supported. Relative local paths are resolved against the config file directory, while inline/stdin configs fall back to the current working directory. JSON $schema metadata is stripped from the in-memory defaults before validation/output so editor hints do not leak into the final config payload.

Remote http(s) schema loading exists only in schemaui-cli, and the CLI enables the remote-schema feature by default. Disable it if you want a local-only binary surface; the schemaui library crate does not enable any remote schema loading by default.

Feature defaults are intentionally split by audience:

  • schemaui-cli defaults to the convenient, batteries-included path: TUI + Web + remote schema loading.
  • schemaui defaults to tui + json, so library consumers keep JSON support without pulling in Web or remote/network-related surface area by default.
  • json, yaml, and toml are real code-level gates. Keep at least one of them enabled; disabling all three triggers a clear compile-time error.

References:

Quick Start

[dependencies]
schemaui = "0.12.4"
serde_json = "1"

use anyhow::Result;
use schemaui::prelude::*;
use serde_json::json;

fn main() -> Result<()> {
    let schema = json!({
        "$schema": "http://json-schema.org/draft-07/schema#",
        "title": "Service Runtime",
        "type": "object",
        "properties": {
            "metadata": {
                "type": "object",
                "properties": {
                    "serviceName": {"type": "string"},
                    "environment": {
                        "type": "string",
                        "enum": ["dev", "staging", "prod"]
                    }
                },
                "required": ["serviceName"]
            },
            "runtime": {
                "type": "object",
                "properties": {
                    "http": {
                        "type": "object",
                        "properties": {
                            "host": {"type": "string", "default": "0.0.0.0"},
                            "port": {"type": "integer", "minimum": 1024, "maximum": 65535}
                        }
                    }
                }
            }
        },
        "required": ["metadata", "runtime"]
    });

    let config = serde_json::json!({
        "metadata": { "name": "demo-service" },
        "runtime": { "http": { "host": "127.0.0.1", "port": 8080 } }
    });

    let value = SchemaUI::new(config)
        .with_schema(schema)
        .with_title("SchemaUI Demo")
        .with_description("Edit an existing config against a validation schema")
        .run(FrontendOptions::Tui(UiOptions::default()))?;
    println!("{}", serde_json::to_string_pretty(&value)?);
    Ok(())
}

Public API surface

For library integrations, the main entry points are:

  • High-level runtime: SchemaUI, DocumentInput, FrontendOptions, ServeOptions, and UiOptions
  • TUI runtime: crate::tui::session::TuiFrontend for custom frontend injection via SchemaUI::run_with_frontend
  • TUI state: crate::tui::state::* (for example FormState, FormCommand, FormEngine, SectionState)
  • Schema backend: crate::ui_ast::build_ui_ast together with crate::tui::model::form_schema_from_ui_ast (builds FormSchema from the canonical UI AST)

Architecture Snapshot

┌─────────────┐   parse/merge    ┌───────────────┐   layout + typing      ┌───────────────┐
│ io::input   ├─────────────────▶│ schema        ├───────────────────────▶│ tui::state    │
└─────────────┘                  │ (loader /     │                        │ (FormState,   │
                                 │ resolver /    │                        │ sections,     │
┌─────────────┐   emit Value     │ build_form_   │   FormSchema           │ reducers)     │
│ io::output  ◀──────────────────┴────pipeline───┘                        └────────┬──────┘
└─────────────┘                                                      focus/edits│
                                                                                │
                                                                     ┌──────────▼──────────┐
                                                                     │ tui::app::runtime   │
                                                                     │ (InputRouter,       │
                                                                     │ overlays, status)   │
                                                                     └──────────┬──────────┘
                                                                                │ draw
                                                                     ┌──────────▼──────────┐
                                                                     │ tui::view::*        │
                                                                     │ (ratatui view)      │
                                                                     └─────────────────────┘

This layout mirrors the actual modules under src/, making it easy to map any code change to its architectural responsibility.

Input & Output Design

  • io::input::parse_document_str converts JSON/YAML/TOML (via serde_json, serde_yaml, toml) into serde_json::Value. Feature flags (json, yaml, toml) keep dependencies lean, and the same gates also drive DocumentFormat parsing/probing at compile time.
  • schema_from_data_value/str infers schemas from live configs, injecting draft-07 metadata and defaults so UIs load pre-existing values.
  • schema_with_defaults merges canonical schemas with user data, propagating defaults through properties, patternProperties, additionalProperties, dependencies, dependentSchemas, arrays, and $ref targets without mutating the original tree.
  • io::output::OutputOptions encapsulates serialization format, pretty/compact toggle, and a vector of OutputDestination::{Stdout, File}. Multiple destinations are supported; conflicts are caught before emission.
  • OutputOptions::render turns the final serde_json::Value into JSON/YAML/TOML text, and OutputOptions::write sends that payload to stdout/files explicitly after SchemaUI::run* returns.

Web UI Mode

Enable the web feature to ship a browser UI (static assets under web/dist/ are embedded in the crate). The same schema/config pipeline used by the TUI feeds a three-pane experience:

  1. Navigation – nested schema tree / breadcrumbs for multi-level objects
  2. Form editor – required flags, enums, numbers, arrays, live field errors
  3. JSON preview – pretty-printed document that updates as you edit

Screenshot: see Surfaces at a Glance (docs/web.mix.png).

CLI (fastest path)

schemaui-cli enables web by default. Same I/O flags as TUI; only host/port are Web-specific:

# random free port on 127.0.0.1; print final JSON to stdout
schemaui web \
  --schema ./schema.json \
  --config ./defaults.json \
  --host 127.0.0.1 --port 0 \
  -o -

# fixed port + write result to disk
schemaui web -s ./schema.json -c ./config.yaml -p 8787 -o ./out.json
Flag Default Meaning
--host / -l 127.0.0.1 Bind address (--bind / --listen aliases)
--port / -p 0 Bind port (0 = ephemeral free port)

Workflow in the browser: edit fields → Save keeps the session open → Save & Exit (or Exit) shuts down the temporary server and emits the value through configured -o destinations.

Full CLI manual: docs/en/cli_usage.md.

Library (embed in your app)

use schemaui::web::session::{
    ServeOptions,
    WebSessionBuilder,
    bind_session,
};

async fn run() -> anyhow::Result<()> {
  let schema = serde_json::json!({
      "$schema": "http://json-schema.org/draft-07/schema#",
      "type": "object",
      "properties": {
          "host": {"type": "string", "default": "127.0.0.1"},
          "port": {"type": "integer", "default": 8080}
      },
      "required": ["host", "port"]
  });

  let config = WebSessionBuilder::new(schema)
      .with_title("Service Config")
      .build()?;
  let session = bind_session(config, ServeOptions::default()).await?;
  println!("visit http://{}/", session.local_addr());
  let value = session.run().await?;
  println!("final JSON: {}", serde_json::to_string_pretty(&value)?);
  Ok(())
}

bind_session / serve_session spawn an Axum router with /api/session, /api/save, /api/exit plus embedded static assets. For custom HTTP stacks, reuse session_router / WebSessionBuilder instead of the turnkey helpers. The CLI schemaui web … command is a thin wrapper around these APIs.

Architecture notes: docs/en/web-ui-architecture-and-refactor-spec.md.

JSON Schema → TUI Mapping

build_ui_ast resolves the schema into the canonical UI AST, and form_schema_from_ui_ast maps that tree into FormSection/FieldSchema for the TUI runtime:

Schema feature Resulting control
type: string, integer, number Inline text editors with numeric guards
type: boolean Toggle/checkbox
enum Popup selector (single or multi-select for array enums)
Arrays Inline list summary + overlay editor per item
patternProperties, propertyNames, additionalProperties Key/Value editor with schema-backed validation
$ref, definitions Resolved before layout; treated like inline schemas
oneOf / anyOf Variant chooser + overlay form, keeps inactive variants out of the final payload

Root objects spawn tabs; nested objects become sections with breadcrumb titles. Every field records its JSON pointer (for example /runtime/http/port) so focus management and validation can map errors back precisely.

Validation Lifecycle

  • jsonschema::validator_for compiles the complete schema once when SchemaUI::run begins.
  • Each edit dispatches FormCommand::FieldEdited. FormEngine rebuilds the current document via FormState::try_build_value, runs the validator, and feeds errors back into FieldState or the global status line.
  • Overlays (composite variants, key/value maps, list entries) spin up their own validators built from the sub-schema currently being edited. Nested overlays live on a stack, so each level validates in place before changes flow back to the parent form.
┌─────────────┐ parse schema ┌─────────────────┐ inflate state  ┌────────────┐
│ SchemaUI::run├────────────▶│ domain::parse   ├───────────────▶│ FormState  │
└─────┬───────┘              │ (schema::layout)│                └─────┬──────┘
      │ validator_for()      └─────────────────┘                edits │
      │                                                        ┌──────▼─────────┐
      └────────────────────────────────────────────────────── ▶│ app::runtime   │
                                                               │ (status, input)│
                                                               └──────┬─────────┘
                                                                      │ FormCommand
                                                               ┌──────▼──────────┐
                                                               │ FormEngine      │
                                                               │ + jsonschema    │
                                                               └─────────────────┘

App is the sole owner of FormState; even overlay edits flow through FormEngine so validation rules stay centralized.

TUI Building Blocks & Shortcuts

  • Single source for shortcuts – keymap/default.keymap.json lists every shortcut (context, combos, action). The app::keymap::keymap_source!() macro pulls this file into the binary, InputRouter uses it to classify KeyEvents, and the runtime footer renders help text from the same data—keeping docs and behavior DRY.
  • Root tabs & sections – focus cycles with Ctrl+J / Ctrl+L (roots) and Ctrl+Tab / Ctrl+Shift+Tab (sections). Ordinary Tab/Shift+Tab walk individual fields.
  • Fields – render labels, descriptions, and inline error messages. Enum/composite fields show the current selection; arrays summarize length and selected entry.
  • Popups & overlays – pressing Enter opens a popup for enums/oneOf selectors; Ctrl+E pushes a full-screen overlay editor for composites, key/value pairs, and array items. Overlays expose collection shortcuts (Ctrl+N, Ctrl+D, Ctrl+←/→, Ctrl+↑/↓), Ctrl+S saves the active level without closing, and Esc / Ctrl+Q pops a single overlay.
  • Status & help – the footer highlights dirty state, outstanding validation errors, and context-aware help text. When auto-validate is enabled, each edit updates these counters immediately.

Generated shortcut reference

Default context

Shortcut Action Kind
Tab / Down Next field command
BackTab / Up Previous field command
Ctrl+Tab Next section command
Ctrl+Shift+Tab Previous section command
Ctrl+L Next root tab command
Ctrl+J Previous root tab command
Enter Open popup / apply selection command
Ctrl+E Open composite editor command
Ctrl+S Save & validate (overlays stay open) command
Ctrl+Q / Ctrl+C Quit (confirm if dirty) command
Esc Cancel / clear status (overlays: pop current level) command
Ctrl+? / Ctrl+H Show help and error summary command

Collection context

Shortcut Action Kind
Ctrl+E Open composite editor command
Ctrl+N Add entry command
Ctrl+D Remove entry command
Ctrl+Left Select previous entry command
Ctrl+Right Select next entry command
Ctrl+Up Move entry up command
Ctrl+Down Move entry down command
Ctrl+? / Ctrl+H Show help and error summary command

Overlay context

Shortcut Action Kind
Tab / Down Next field command
BackTab / Up Previous field command
Ctrl+N Add entry command
Ctrl+D Remove entry command
Ctrl+Left Select previous entry command
Ctrl+Right Select next entry command
Ctrl+Up Move entry up command
Ctrl+Down Move entry down command
Ctrl+S Save & validate (overlays stay open) command
Esc Cancel / clear status (overlays: pop current level) command
Ctrl+? / Ctrl+H Show help and error summary command

Popup context

Shortcut Action Kind
Esc Close popup command
Up Select previous popup option command
Down Select next popup option command
Space Toggle popup option command
Enter Apply popup selection command

Help context

Shortcut Action Kind
Esc / Ctrl+H / Ctrl+? Close help command
Tab Next error page command
BackTab Previous error page command
Up / k Scroll shortcuts up command
Down / j Scroll shortcuts down command
PageUp Page shortcuts up command
PageDown Page shortcuts down command
Home Jump shortcuts to top command
End Jump shortcuts to bottom command
h Scroll error text left command
l Scroll error text right command

Text field context

Shortcut Action Kind
Left Move cursor left local edit
Right Move cursor right local edit
Home Jump to line start local edit
End Jump to line end local edit
Backspace Delete previous character local edit
Delete Delete next character local edit
Ctrl+W Delete previous word local edit
Ctrl+Z Undo text edit local edit
Ctrl+Y Redo text edit local edit

Numeric field context

Shortcut Action Kind
Left Step value down local edit
Right Step value up local edit
Shift+Left Fast step value down local edit
Shift+Right Fast step value up local edit
Backspace Delete previous character local edit
Delete Delete next character local edit
Ctrl+Z Undo numeric edit local edit
Ctrl+Y Redo numeric edit local edit

Boolean field context

Shortcut Action Kind
Space / Left / Right Toggle boolean value local edit
Enter Open popup / apply selection command

Enum field context

Shortcut Action Kind
Up / Left Previous enum option local edit
Down / Right Next enum option local edit
Enter Open popup / apply selection command

Multi-select field context

Shortcut Action Kind
Enter Open popup / apply selection command

Composite field context

Shortcut Action Kind
Left Previous composite variant local edit
Right Next composite variant local edit
Enter Open popup / apply selection command

Array buffer field context

Shortcut Action Kind
Backspace Delete previous array buffer character local edit
Delete Clear array buffer local edit

Keymap system

Put every shortcut into keymap/default.keymap.json, so runtime logic, help overlays, and generated README shortcut references all consume a single source of truth.

  • Format – each JSON object declares an id, human-readable description, bilingual descriptionZh, contexts (any of "default", "collection", "overlay", "popup", "help", "text", "numeric", "boolean", "enum", "multiSelect", "composite", "arrayBuffer"), an action discriminated union, and a list of textual combos. For example:

    {
  "id": "list.move.up",
  "description": "Move entry up",
  "descriptionZh": "条目上移",
  "contexts": ["collection", "overlay"],
  "action": { "kind": "ListMove", "delta": -1 },
  "combos": ["Ctrl+Up"]
}

  • Macro + parser – app::keymap::keymap_source!() include_str!s the JSON, once_cell::sync::Lazy parses it once at startup, and each combo is compiled into a KeyPattern (key code, required modifiers, pretty display string).

  • Integration – InputRouter::classify delegates to keymap::classify_key, which returns the KeyAction embedded in the JSON. keymap::help_text filters bindings by KeymapContext, concatenating snippets used by StatusLine and overlay instructions.

  • Generated docs – build.rs parses keymap/default.keymap.json and refreshes the shortcut blocks in README.md and README.ZH.md using explicit HTML markers, so normal Cargo builds keep the bilingual reference in sync with runtime behavior.

  • Extending – to add a shortcut, edit the JSON, choose the contexts that should expose the help text, and wire the resulting KeyAction inside KeyBindingMap if a new semantic command is introduced.

Runtime Layers

Layer Module(s) Responsibilities
Ingestion io::input, schema::loader, schema::resolver Parse JSON/TOML/YAML, resolve $ref, and normalize metadata.
Layout typing ui_ast::build_ui_ast, tui::model::form_schema_from_ui_ast Produce FormSchema (roots/sections/fields) from the canonical UI AST.
Form state tui::state::{form_state, section, field} Track focus, pointers, dirty flags, coercions, and errors.
Commands & reducers tui::state::{actions, reducers}, tui::app::validation Define FormCommand, mutate state, and route validation results.
Runtime controller tui::app::{runtime, overlay, popup, status, keymap} Event loop, InputRouter dispatch, overlay lifecycle, help text, status updates.
Presentation tui::view and tui::view::components::* Render tabs, field lists, popups, overlays, and footer via ratatui.

Each module is kept under ~600 LOC (hard cap 800) to honor the KISS principle and make refactors manageable.

CLI (schemaui-cli)

Install

The installed binary is always named schemaui, so the normal entry point is schemaui -c ./config.json.

Choose one of the supported channels:

Cargo (cargo install)

Build from crates.io with Cargo.

cargo install schemaui-cli

Cargo binstall

Fetch prebuilt GitHub release binaries through cargo-binstall.

cargo binstall schemaui-cli

Homebrew

Install from the repository tap on macOS or Linux.

brew install YuniqueUnic/schemaui/schemaui

Scoop

Install on Windows from the repository-hosted Scoop manifest.

scoop install https://raw.githubusercontent.com/YuniqueUnic/schemaui/main/packaging/scoop/schemaui-cli.json

Direct download

Download the matching archive from https://github.com/YuniqueUnic/schemaui/releases/latest, extract schemaui / schemaui.exe, and place it on your PATH.

winget manifests

Use the versioned manifests in packaging/winget with winget install --manifest <dir>, or submit them upstream to the community repository.

Modes (subcommands)

The installed binary is schemaui. If you omit a mode subcommand, it defaults to the TUI. Explicit modes:

Command Purpose
schemaui / schemaui tui Interactive terminal editor (default)
schemaui web Interactive browser editor (embedded HTTP server)
schemaui tui-snapshot Precompute TUI FormSchema/layout artifacts (no UI)
schemaui web-snapshot Precompute Web session snapshots JSON/TS (no UI)
schemaui completion <shell> Shell completions (completion feature) 
# equivalent TUI launches
schemaui --schema ./schema.json --config ./defaults.yaml
schemaui tui --schema ./schema.json --config ./defaults.yaml

# Web UI (see also Web UI Mode above)
schemaui web --schema ./schema.json --config ./defaults.yaml --port 0 -o -

Typical TUI pipeline

schemaui \
  --schema ./schema.json \
  --config ./defaults.yaml \
  -o - \
  -o ./config.toml ./config.json

┌────────┐  clap args   ┌──────────────┐ read stdin/files ┌─────────────┐
│  CLI   ├─────────────▶│ InputSource  ├─────────────────▶│ io::input   │
└────┬───┘              └──────┬───────┘                  └────┬────────┘
     │ diagnostics             │ schema/default Value          │
┌────▼─────────┐        ┌──────▼──────┐                        |
│Diagnostic    │◀───────┤ FormatHint  │                        │
│Collector     │        └──────┬──────┘                        │
└────┬─────────┘               │ pass if clean                 │
     │                         │                               │
┌────▼────────┐  build options └────────────┐                  │
│Output logic ├────────────────────────────▶│ OutputOptions    │
└────┬────────┘                             └────────────┬─────┘
     │ SchemaUI::new / with_*                        ┌───▼────────┐
     └──────────────────────────────────────────────▶│ SchemaUI   │
                                                     │ (library)  │
                                                     └────────────┘

Shared I/O contract (TUI and Web)

  • Inputs – --schema / --config accept file paths, file:// or http(s) URLs (CLI remote-schema), inline payloads, or - for stdin (not both schema and config on stdin at once). Config-only runs infer a schema via schema_from_data_value (or embedded $schema / #:schema / YAML modeline).
  • Diagnostics – DiagnosticCollector gathers format issues, feature-flag mismatches, stdin conflicts, and existing output files before the UI runs.
  • Outputs – -o/--output is repeatable and may mix file paths with - for stdout. With no destination, the tool writes to stdout; use --temp-file <PATH> for an explicit fallback file. Extensions pick the format; conflicting extensions are rejected.
  • Common flags – --no-pretty (compact), --force / --yes (overwrite), --title / --description (forwarded to the UI).
  • Web-only flags – --host / -l (default 127.0.0.1), --port / -p (default 0 = free port).
  • Shell completion – schemaui completion <bash|zsh|fish|powershell> (requires the completion feature).

Deep dive: docs/en/cli_usage.md · Chinese: docs/zh/cli_usage.zh.md.

Key Dependencies

Crate Purpose
serde, serde_json, serde_yaml, toml Parsing and serializing schema/config data.
schemars Draft-07 schema representation used by the schema module.
jsonschema Runtime validation for forms and overlays.
ratatui Rendering widgets, layouts, overlays, and footer.
crossterm Terminal events consumed by InputRouter.
indexmap Order-preserving maps for schema traversal.
once_cell Lazy parsing of the keymap JSON.
clap, clap_complete, anyhow (CLI) Argument parsing, shell completion, and ergonomic diagnostics.

Documentation Map

  • README.md – overview + architecture snapshot (source of truth).
  • README.ZH.md – Chinese overview kept in sync with this README.
  • docs/en/structure_design.md – detailed schema/layout/runtime design with flow diagrams.
  • docs/zh/structure_design.md – Chinese mirror of the architecture guide.
  • docs/en/cli_usage.md – CLI-specific manual (inputs, outputs, piping, TUI/Web modes, samples).
  • docs/zh/cli_usage.zh.md – Chinese mirror of the CLI usage guide.
  • docs/en/web-ui-architecture-and-refactor-spec.md – Web UI architecture.
  • docs/web.mix.png – Web UI screenshot (schema form + live JSON preview).

Development

  • Run cargo fmt && cargo test regularly; most modules embed their tests by include!ing files from tests/ so private APIs stay covered.
  • Keep modules below ~600 LOC (hard cap 800). Split helpers as soon as behavior grows to keep KISS intact.
  • Prefer mature crates (serde_*, schemars, jsonschema, ratatui, crossterm) over bespoke code unless the change is trivial.
  • Update docs/* whenever pipelines, shortcuts, or CLI semantics evolve so user-facing documentation stays truthful.

References

  1. https://github.com/rjsf-team/react-jsonschema-form
  2. https://ui-schema.bemit.codes/examples

Roadmap

  • parse json schema at runtime and generate a TUI
  • parse json schema at runtime and generate a Web UI
  • parse json schema at compile time Then generate the code for TUI, expose necessary APIs for runtime.
  • parse json schema at compile time Then generate the code for Web UI, expose necessary APIs for runtime.
  • parse json schema at runtime and generate a Interactive CLI
  • parse json schema at compile time Then generate the code for Interactive CLI, expose necessary APIs for runtime.

Licensed under either of

at your option.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Happy hacking!

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