style: Prefer nullish coalescing ?? over ||

.eslintrc.yaml

@@ -32,6 +32,7 @@ rules:
   '@typescript-eslint/no-unsafe-member-access': off
   '@typescript-eslint/no-unused-vars': [warn, argsIgnorePattern: '^_']
   '@typescript-eslint/prefer-includes': warn
+  '@typescript-eslint/prefer-nullish-coalescing': warn
   '@typescript-eslint/prefer-optional-chain': warn
   '@typescript-eslint/restrict-template-expressions': off
 

src/compose/compose-doc.ts

@@ -31,7 +31,7 @@ export function composeDoc(
   }
   const props = resolveProps(start, {
     indicator: 'doc-start',
-    next: value || end?.[0],
+    next: value ?? end?.[0],
     offset,
     onError,
     startOnNewline: true

src/compose/compose-scalar.ts

@@ -35,13 +35,13 @@ export function composeScalar(
   try {
     const res = tag.resolve(
       value,
-      msg => onError(tagToken || token, 'TAG_RESOLVE_FAILED', msg),
+      msg => onError(tagToken ?? token, 'TAG_RESOLVE_FAILED', msg),
       ctx.options
     )
     scalar = isScalar(res) ? res : new Scalar(res)
   } catch (error) {
     const msg = error instanceof Error ? error.message : String(error)
-    onError(tagToken || token, 'TAG_RESOLVE_FAILED', msg)
+    onError(tagToken ?? token, 'TAG_RESOLVE_FAILED', msg)
     scalar = new Scalar(value)
   }
   scalar.range = range
@@ -99,7 +99,7 @@ function findScalarTagByTest(
 
   if (schema.compat) {
     const compat =
-      schema.compat.find(tag => tag.default && tag.test?.test(value)) ||
+      schema.compat.find(tag => tag.default && tag.test?.test(value)) ??
       schema[SCALAR]
     if (tag.tag !== compat.tag) {
       const ts = directives.tagString(tag.tag)

src/compose/composer.ts

@@ -79,6 +79,7 @@ export class Composer {
   private warnings: YAMLWarning[] = []
 
   constructor(options: ParseOptions & DocumentOptions & SchemaOptions = {}) {
+    // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
     this.directives = new Directives({ version: options.version || '1.2' })
     this.options = options
   }

src/compose/resolve-block-map.ts

@@ -27,7 +27,7 @@ export function resolveBlockMap(
     // key properties
     const keyProps = resolveProps(start, {
       indicator: 'explicit-key-ind',
-      next: key || sep?.[0],
+      next: key ?? sep?.[0],
       offset,
       onError,
       startOnNewline: true
@@ -72,7 +72,7 @@ export function resolveBlockMap(
       onError(keyStart, 'DUPLICATE_KEY', 'Map keys must be unique')
 
     // value properties
-    const valueProps = resolveProps(sep || [], {
+    const valueProps = resolveProps(sep ?? [], {
       indicator: 'map-value-ind',
       next: value,
       offset: keyNode.range[2],

src/compose/resolve-flow-collection.ts

@@ -37,7 +37,7 @@ export function resolveFlowCollection(
     const props = resolveProps(start, {
       flow: fcName,
       indicator: 'explicit-key-ind',
-      next: key || sep?.[0],
+      next: key ?? sep?.[0],
       offset,
       onError,
       startOnNewline: false
@@ -92,7 +92,7 @@ export function resolveFlowCollection(
         }
         if (prevItemComment) {
           let prev = coll.items[coll.items.length - 1]
-          if (isPair(prev)) prev = prev.value || prev.key
+          if (isPair(prev)) prev = prev.value ?? prev.key
           if (prev.comment) prev.comment += '\n' + prevItemComment
           else prev.comment = prevItemComment
           props.comment = props.comment.substring(prevItemComment.length + 1)
@@ -120,7 +120,7 @@ export function resolveFlowCollection(
       if (isBlock(key)) onError(keyNode.range, 'BLOCK_IN_FLOW', blockMsg)
 
       // value properties
-      const valueProps = resolveProps(sep || [], {
+      const valueProps = resolveProps(sep ?? [], {
         flow: fcName,
         indicator: 'map-value-ind',
         next: value,

src/compose/resolve-props.ts

@@ -2,7 +2,7 @@ import type { SourceToken, Token } from '../parse/cst.js'
 import type { ComposeErrorHandler } from './composer.js'
 
 export interface ResolvePropsArg {
-  flow?: string
+  flow?: 'flow map' | 'flow sequence'
   indicator: 'doc-start' | 'explicit-key-ind' | 'map-value-ind' | 'seq-item-ind'
   next: Token | null | undefined
   offset: number
@@ -119,7 +119,7 @@ export function resolveProps(
           onError(
             token,
             'UNEXPECTED_TOKEN',
-            `Unexpected ${token.source} in ${flow || 'collection'}`
+            `Unexpected ${token.source} in ${flow ?? 'collection'}`
           )
         found = token
         atNewline = false

src/doc/Document.ts

@@ -182,6 +182,7 @@ export class Document<T = unknown> {
     if (!node.anchor) {
       const prev = anchorNames(this)
       node.anchor =
+        // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
         !name || prev.has(name) ? findNewAnchor(name || 'a', prev) : name
     }
     return new Alias(node.anchor)
@@ -224,9 +225,10 @@ export class Document<T = unknown> {
       keepUndefined,
       onTagObj,
       tag
-    } = options || {}
+    } = options ?? {}
     const { onAnchor, setAnchors, sourceObjects } = createNodeAnchors(
       this,
+      // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
       anchorPrefix || 'a'
     )
     const ctx: CreateNodeContext = {
@@ -423,7 +425,7 @@ export class Document<T = unknown> {
       maxAliasCount: typeof maxAliasCount === 'number' ? maxAliasCount : 100,
       stringify
     }
-    const res = toJS(this.contents, jsonArg || '', ctx)
+    const res = toJS(this.contents, jsonArg ?? '', ctx)
     if (typeof onAnchor === 'function')
       for (const { count, res } of ctx.anchors.values()) onAnchor(res, count)
     return typeof reviver === 'function'

src/doc/createNode.ts

@@ -25,7 +25,7 @@ function findTagObject(
 ) {
   if (tagName) {
     const match = tags.filter(t => t.tag === tagName)
-    const tagObj = match.find(t => !t.format) || match[0]
+    const tagObj = match.find(t => !t.format) ?? match[0]
     if (!tagObj) throw new Error(`Tag ${tagName} not found`)
     return tagObj
   }

src/parse/lexer.ts

@@ -178,7 +178,7 @@ export class Lexer {
       this.lineEndPos = null
     }
     this.atEnd = !incomplete
-    let next: State | null = this.next || 'stream'
+    let next: State | null = this.next ?? 'stream'
     while (next && (incomplete || this.hasChars(1)))
       next = yield* this.parseNext(next)
   }

src/parse/parser.ts

@@ -54,7 +54,7 @@ function getPrevProps(parent: Token) {
       return parent.start
     case 'block-map': {
       const it = parent.items[parent.items.length - 1]
-      return it.sep || it.start
+      return it.sep ?? it.start
     }
     case 'block-seq':
       return parent.items[parent.items.length - 1].start
@@ -291,7 +291,7 @@ export class Parser {
   }
 
   private *pop(error?: Token): Generator<Token, void> {
-    const token = error || this.stack.pop()
+    const token = error ?? this.stack.pop()
     /* istanbul ignore if should not happen */
     if (!token) {
       const message = 'Tried to pop an empty stack'

src/public-api.ts

@@ -202,7 +202,7 @@ export function stringify(
     options = indent < 1 ? undefined : indent > 8 ? { indent: 8 } : { indent }
   }
   if (value === undefined) {
-    const { keepUndefined } = options || (replacer as CreateNodeOptions) || {}
+    const { keepUndefined } = options ?? (replacer as CreateNodeOptions) ?? {}
     if (!keepUndefined) return undefined
   }
   return new Document(value, _replacer, options).toString(options)

src/schema/Schema.ts

@@ -42,15 +42,19 @@ export class Schema {
     this.name = (typeof schema === 'string' && schema) || 'core'
     this.knownTags = resolveKnownTags ? coreKnownTags : {}
     this.tags = getTags(customTags, this.name)
-    this.toStringOptions = toStringDefaults || null
+    this.toStringOptions = toStringDefaults ?? null
 
     Object.defineProperty(this, MAP, { value: map })
     Object.defineProperty(this, SCALAR, { value: string })
     Object.defineProperty(this, SEQ, { value: seq })
 
     // Used by createMap()
     this.sortMapEntries =
-      sortMapEntries === true ? sortMapEntriesByKey : sortMapEntries || null
+      typeof sortMapEntries === 'function'
+        ? sortMapEntries
+        : sortMapEntries === true
+        ? sortMapEntriesByKey
+        : null
   }
 
   clone(): Schema {

src/schema/yaml-1.1/pairs.ts

@@ -27,7 +27,7 @@ export function resolvePairs(
             ? `${item.commentBefore}\n${pair.key.commentBefore}`
             : item.commentBefore
         if (item.comment) {
-          const cn = pair.value || pair.key
+          const cn = pair.value ?? pair.key
           cn.comment = cn.comment
             ? `${item.comment}\n${cn.comment}`
             : item.comment

src/stringify/stringify.ts

@@ -86,7 +86,7 @@ function getTagObject(tags: Array<ScalarTag | CollectionTag>, item: Node) {
   if (item.tag) {
     const match = tags.filter(t => t.tag === item.tag)
     if (match.length > 0)
-      return match.find(t => t.format === (item as Scalar).format) || match[0]
+      return match.find(t => t.format === (item as Scalar).format) ?? match[0]
   }
 
   let tagObj: ScalarTag | CollectionTag | undefined = undefined
@@ -95,7 +95,7 @@ function getTagObject(tags: Array<ScalarTag | CollectionTag>, item: Node) {
     obj = item.value
     const match = tags.filter(t => t.identify?.(obj))
     tagObj =
-      match.find(t => t.format === item.format) || match.find(t => !t.format)
+      match.find(t => t.format === item.format) ?? match.find(t => !t.format)
   } else {
     obj = item
     tagObj = tags.find(t => t.nodeClass && obj instanceof t.nodeClass)
@@ -121,7 +121,7 @@ function stringifyProps(
     anchors.add(anchor)
     props.push(`&${anchor}`)
   }
-  const tag = node.tag || (tagObj.default ? null : tagObj.tag)
+  const tag = node.tag ? node.tag : tagObj.default ? null : tagObj.tag
   if (tag) props.push(doc.directives.tagString(tag))
   return props.join(' ')
 }
@@ -156,7 +156,7 @@ export function stringify(
 
   const props = stringifyProps(node, tagObj, ctx)
   if (props.length > 0)
-    ctx.indentAtStart = (ctx.indentAtStart || 0) + props.length + 1
+    ctx.indentAtStart = (ctx.indentAtStart ?? 0) + props.length + 1
 
   const str =
     typeof tagObj.stringify === 'function'

src/test-events.ts

@@ -66,7 +66,7 @@ export function testEvents(src: string) {
       events.push(docEnd)
     }
   } catch (e) {
-    return { events, error: error || e }
+    return { events, error: error ?? e }
   }
   events.push('-STR')
   return { events, error }