phase 11: plumbing prereqs — Wiki, edits, config, snapshot, diags

Cross-cutting infrastructure that every v1.1 phase depends on. Lands as
a numbered phase before any user-visible feature so Phases 12–19 stay
mechanical.

5 pieces:

- `config.rs` — `Config` + `WikiConfig` + `DiagnosticConfig` + `LinkSeverity`.
  Serde-deserialised from `initialization_options`. v1.0 single-wiki
  shape (`wiki_root` + `file_extension` + `syntax`) desugars to one-entry
  `wikis = [...]` per P16. `~/...` expansion without pulling in `dirs`.
  Fallbacks: workspace_folders[0] → deprecated root_uri → empty list.

- `wiki.rs` — `Wiki` aggregate (id + WikiConfig + Arc<RwLock<Index>>).
  `build_wikis(&[WikiConfig])` materialises the list; `resolve_uri_to_wiki`
  picks the longest-prefix root match so nested wikis route correctly.
  Single-entry today, multi-entry once Phase 18 lands.

- `edits.rs` — `WorkspaceEditBuilder` + `text_edit_replace/insert/delete`
  + `op_rename/delete/create`. Handles the UTF-8/UTF-16 conversion at the
  span boundary so each Phase 13+ command stays a 3-liner. Builder picks
  `documentChanges` when file ops are present (LSP requires it), `changes`
  map otherwise (works for LSP 3.15- clients). File ops precede content
  edits in the output so created/renamed files exist when edits apply.
  `DeleteFile` is built without `annotation_id` — lsp-types 0.94.x ships
  it that way; later versions added the field.

- `Backend` refactor — `index: Arc<RwLock<WorkspaceIndex>>` replaced by
  `wikis: Arc<RwLock<Vec<Wiki>>>` + `config: Arc<RwLock<Config>>`. New
  `wiki(id)` / `default_wiki()` / `wiki_for_uri(uri)` helpers. Every v1.0
  handler (definition, references, hover, completion, workspace/symbol,
  update_document) goes through `wiki_for_uri`. `initialize` builds wikis
  from `Config::from_init_params`; `initialized` spawns one indexer task
  per wiki with the existing `window/workDoneProgress` wrapper. New
  `did_change_configuration` handler re-applies settings (rebuild
  semantics revisited in Phase 18). The old `workspace_root_from_params`
  helper is gone.

- `read_or_open` + `DocSnapshot` (scaffolded, `#[allow(dead_code)]` until
  Phase 13's `workspace/rename` consumes it). Returns the live document
  when held in the documents map, otherwise async-reads from disk and
  re-parses so cross-document operations get accurate text and spans
  instead of trusting stale `WorkspaceIndex` data.

- `collect_diagnostics` composable collector. Same `ErrorNode` walk
  today; takes `Option<&WorkspaceIndex>` + `page_name` + `&DiagnosticConfig`
  so Phase 15 can drop a link-health source in without further refactor.
  `ast_diagnostics` kept as a thin wrapper for the v1.0 test surface.

New deps: `serde` + `serde_json` (already transitive through tower-lsp;
elevated to direct deps for clarity and stability). `tokio` gains the
`fs` feature for `read_or_open`'s async disk read.

Tests (19 new in `phase11_plumbing.rs`):
- Edits: UTF-8 passthrough + UTF-16 conversion (`héllo`), insert/delete
  shape, builder mode selection, file-op accumulation, `op_create` round-trip
- Config: defaults, v1.0 desugar, explicit list overrides legacy, empty
  JSON, invalid JSON preserves prior state
- Wiki: sequential id assignment, longest-prefix resolution, no-match,
  `Wiki::contains`
- Diagnostics: error-node composition, link-health stub returns empty in
  Phase 11

All 172 v1.0 tests still pass — backward compatible.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/tests/phase11_plumbing.rs

@@ -0,0 +1,260 @@
+//! Phase 11 plumbing tests: WorkspaceEditBuilder, Config desugar, Wiki
+//! resolution, collect_diagnostics composition. The async closed-doc
+//! loader (`Backend::read_or_open`) is exercised via integration of the
+//! pure pieces — the full handler path is exercised once Phase 13 wires
+//! it into `workspace/rename`.
+
+use std::path::PathBuf;
+
+use nuwiki_core::ast::{
+    inline::InlineNode, BlockNode, DocumentNode, ErrorNode, ParagraphNode, Position as AstPosition,
+    Span, TextNode,
+};
+use nuwiki_lsp::collect_diagnostics;
+use nuwiki_lsp::config::{config_from_json, Config, DiagnosticConfig, LinkSeverity, WikiConfig};
+use nuwiki_lsp::edits::{
+    op_create, op_delete, op_rename, text_edit_delete, text_edit_insert, text_edit_replace,
+    WorkspaceEditBuilder,
+};
+use nuwiki_lsp::wiki::{build_wikis, resolve_uri_to_wiki, Wiki, WikiId};
+use serde_json::json;
+use tower_lsp::lsp_types::{DocumentChanges, Position as LspPosition, Url};
+
+// ===== Edits =====
+
+fn span_one_line(byte_col: u32, len: u32) -> Span {
+    Span::new(
+        AstPosition {
+            line: 0,
+            column: byte_col,
+            offset: byte_col as usize,
+        },
+        AstPosition {
+            line: 0,
+            column: byte_col + len,
+            offset: (byte_col + len) as usize,
+        },
+    )
+}
+
+#[test]
+fn text_edit_replace_passthrough_in_utf8() {
+    let edit = text_edit_replace(span_one_line(0, 5), "world".into(), "hello there", true);
+    assert_eq!(edit.range.start.character, 0);
+    assert_eq!(edit.range.end.character, 5);
+    assert_eq!(edit.new_text, "world");
+}
+
+#[test]
+fn text_edit_replace_converts_to_utf16_for_multibyte() {
+    // "héllo" — h(1B) é(2B) l(1B) l(1B) o(1B); UTF-16 chars: 1+1+1+1+1=5.
+    // span covers bytes 0..3 (h + é); UTF-16 character count = 2.
+    let edit = text_edit_replace(span_one_line(0, 3), "X".into(), "héllo", false);
+    assert_eq!(edit.range.start.character, 0);
+    assert_eq!(edit.range.end.character, 2);
+}
+
+#[test]
+fn text_edit_insert_produces_zero_width_range() {
+    let edit = text_edit_insert(
+        LspPosition {
+            line: 0,
+            character: 4,
+        },
+        "X".into(),
+    );
+    assert_eq!(edit.range.start, edit.range.end);
+    assert_eq!(edit.new_text, "X");
+}
+
+#[test]
+fn text_edit_delete_has_empty_new_text() {
+    let edit = text_edit_delete(span_one_line(0, 3), "abcdef", true);
+    assert_eq!(edit.new_text, "");
+    assert_eq!(edit.range.end.character, 3);
+}
+
+#[test]
+fn builder_with_only_edits_uses_changes_map() {
+    let uri = Url::parse("file:///tmp/a.wiki").unwrap();
+    let mut b = WorkspaceEditBuilder::new();
+    b.edit(
+        uri.clone(),
+        text_edit_replace(span_one_line(0, 3), "new".into(), "old text", true),
+    );
+    let we = b.build();
+    assert!(we.changes.is_some());
+    assert!(we.document_changes.is_none());
+    let changes = we.changes.unwrap();
+    assert_eq!(changes.len(), 1);
+    assert_eq!(changes[&uri].len(), 1);
+}
+
+#[test]
+fn builder_with_file_op_promotes_to_document_changes() {
+    let old = Url::parse("file:///tmp/A.wiki").unwrap();
+    let new = Url::parse("file:///tmp/B.wiki").unwrap();
+    let mut b = WorkspaceEditBuilder::new();
+    b.file_op(op_rename(old.clone(), new.clone()));
+    b.edit(
+        new.clone(),
+        text_edit_replace(span_one_line(0, 1), "X".into(), "Y", true),
+    );
+    let we = b.build();
+    assert!(we.changes.is_none());
+    let DocumentChanges::Operations(ops) = we.document_changes.unwrap() else {
+        panic!("expected Operations variant");
+    };
+    // Rename comes first (file ops always precede content edits in the
+    // builder), then the text edit on the renamed file.
+    assert_eq!(ops.len(), 2);
+}
+
+#[test]
+fn builder_is_empty_until_something_pushed() {
+    let mut b = WorkspaceEditBuilder::new();
+    assert!(b.is_empty());
+    b.file_op(op_delete(Url::parse("file:///x").unwrap()));
+    assert!(!b.is_empty());
+}
+
+#[test]
+fn op_create_round_trips_through_builder() {
+    let uri = Url::parse("file:///tmp/new.wiki").unwrap();
+    let mut b = WorkspaceEditBuilder::new();
+    b.file_op(op_create(uri));
+    let we = b.build();
+    assert!(we.document_changes.is_some());
+}
+
+// ===== Config =====
+
+#[test]
+fn config_default_is_empty() {
+    let c = Config::default();
+    assert!(c.wikis.is_empty());
+    assert_eq!(c.diagnostic.link_severity, LinkSeverity::Warning);
+}
+
+#[test]
+fn v1_0_single_wiki_desugars_to_one_entry() {
+    let cfg = config_from_json(json!({
+        "wiki_root": "/tmp/vimwiki",
+        "file_extension": ".wiki",
+        "syntax": "vimwiki",
+    }));
+    assert_eq!(cfg.wikis.len(), 1);
+    assert_eq!(cfg.wikis[0].root, PathBuf::from("/tmp/vimwiki"));
+    assert_eq!(cfg.wikis[0].file_extension, ".wiki");
+    assert_eq!(cfg.wikis[0].syntax, "vimwiki");
+}
+
+#[test]
+fn explicit_wikis_list_overrides_legacy_shape() {
+    let cfg = config_from_json(json!({
+        "wiki_root": "/tmp/IGNORED",
+        "wikis": [
+            { "root": "/tmp/personal", "name": "personal" },
+            { "root": "/tmp/work", "syntax": "vimwiki" },
+        ],
+    }));
+    assert_eq!(cfg.wikis.len(), 2);
+    assert_eq!(cfg.wikis[0].name, "personal");
+    assert_eq!(cfg.wikis[1].root, PathBuf::from("/tmp/work"));
+}
+
+#[test]
+fn empty_json_yields_no_wikis() {
+    let cfg = config_from_json(json!({}));
+    assert!(cfg.wikis.is_empty());
+}
+
+#[test]
+fn invalid_json_leaves_existing_config_unchanged() {
+    let mut cfg = Config::default();
+    cfg.wikis
+        .push(WikiConfig::from_root(PathBuf::from("/tmp/a")));
+    cfg.apply_change(&json!("not a config object"));
+    // Existing wikis still present.
+    assert_eq!(cfg.wikis.len(), 1);
+}
+
+// ===== Wiki aggregate =====
+
+fn wiki_at(id: u32, root: &str) -> Wiki {
+    Wiki::new(WikiId(id), WikiConfig::from_root(PathBuf::from(root)))
+}
+
+#[test]
+fn build_wikis_assigns_sequential_ids() {
+    let configs = vec![
+        WikiConfig::from_root(PathBuf::from("/tmp/a")),
+        WikiConfig::from_root(PathBuf::from("/tmp/b")),
+    ];
+    let wikis = build_wikis(&configs);
+    assert_eq!(wikis.len(), 2);
+    assert_eq!(wikis[0].id, WikiId(0));
+    assert_eq!(wikis[1].id, WikiId(1));
+}
+
+#[test]
+fn resolve_uri_to_wiki_picks_longest_prefix() {
+    let wikis = vec![wiki_at(0, "/wiki"), wiki_at(1, "/wiki/sub")];
+    let uri = Url::from_file_path("/wiki/sub/page.wiki").unwrap();
+    assert_eq!(resolve_uri_to_wiki(&wikis, &uri), Some(WikiId(1)));
+}
+
+#[test]
+fn resolve_uri_to_wiki_misses_outside_any_root() {
+    let wikis = vec![wiki_at(0, "/wiki")];
+    let uri = Url::from_file_path("/other/page.wiki").unwrap();
+    assert!(resolve_uri_to_wiki(&wikis, &uri).is_none());
+}
+
+#[test]
+fn wiki_contains_respects_root_prefix() {
+    let w = wiki_at(0, "/wiki");
+    assert!(w.contains(&Url::from_file_path("/wiki/note.wiki").unwrap()));
+    assert!(!w.contains(&Url::from_file_path("/other/note.wiki").unwrap()));
+}
+
+// ===== Diagnostics composition =====
+
+#[test]
+fn collect_diagnostics_emits_one_per_error_node() {
+    let doc = DocumentNode {
+        span: Span::default(),
+        metadata: Default::default(),
+        children: vec![
+            BlockNode::Error(ErrorNode {
+                span: span_one_line(0, 3),
+                raw: "oops".into(),
+                message: "broken".into(),
+            }),
+            BlockNode::Paragraph(ParagraphNode {
+                span: Span::default(),
+                children: vec![InlineNode::Text(TextNode {
+                    span: Span::default(),
+                    content: "ok".into(),
+                })],
+            }),
+        ],
+    };
+    let cfg = DiagnosticConfig::default();
+    let diags = collect_diagnostics(&doc, "abc ok", None, None, &cfg, true);
+    assert_eq!(diags.len(), 1);
+    assert_eq!(diags[0].message, "broken");
+}
+
+#[test]
+fn collect_diagnostics_link_health_stubs_to_empty_in_phase_11() {
+    // With an index supplied but the link-health source not yet wired in,
+    // we should still get zero link-related diagnostics (Phase 15 wires
+    // them in).
+    let doc = DocumentNode::default();
+    let cfg = DiagnosticConfig {
+        link_severity: LinkSeverity::Error,
+    };
+    let diags = collect_diagnostics(&doc, "", None, Some("Home"), &cfg, true);
+    assert!(diags.is_empty());
+}