feat: improve props type (#435)

Author: ota-meshi

Diff for: .changeset/yellow-cooks-end.md

@@ -0,0 +1,5 @@
+---
+"svelte-eslint-parser": minor
+---
+
+feat: improve props type

Diff for: src/parser/converts/attr.ts

@@ -33,6 +33,7 @@ import {
 import { ParseError } from "../../errors";
 import type { ScriptLetCallback } from "../../context/script-let";
 import type { AttributeToken } from "../html";
+import { svelteVersion } from "../svelte-version";
 
 /** Convert for Attributes */
 export function* convertAttributes(
@@ -200,6 +201,7 @@ function convertAttribute(
   processAttributeValue(
     node.value as (SvAST.Text | SvAST.MustacheTag)[],
     attribute,
+    parent,
     ctx,
   );
 
@@ -213,27 +215,51 @@ function convertAttribute(
 function processAttributeValue(
   nodeValue: (SvAST.Text | SvAST.MustacheTag)[],
   attribute: SvelteAttribute | SvelteStyleDirectiveLongform,
+  attributeParent: (SvelteAttribute | SvelteStyleDirectiveLongform)["parent"],
   ctx: Context,
 ) {
-  for (let index = 0; index < nodeValue.length; index++) {
-    const v = nodeValue[index];
-    if (v.type === "Text") {
-      if (v.start === v.end) {
-        // Empty
+  const nodes = nodeValue
+    .filter(
+      (v) =>
+        v.type !== "Text" ||
+        // ignore empty
         // https://github.com/sveltejs/svelte/pull/6539
-        continue;
-      }
-      const next = nodeValue[index + 1];
-      if (next && next.start < v.end) {
-        // Maybe bug in Svelte can cause the completion index to shift.
-        // console.log(ctx.getText(v), v.data)
-        v.end = next.start;
+        v.start < v.end,
+    )
+    .map((v, index, array) => {
+      if (v.type === "Text") {
+        const next = array[index + 1];
+        if (next && next.start < v.end) {
+          // Maybe bug in Svelte can cause the completion index to shift.
+          return {
+            ...v,
+            end: next.start,
+          };
+        }
       }
+      return v;
+    });
+  if (
+    nodes.length === 1 &&
+    nodes[0].type === "MustacheTag" &&
+    attribute.type === "SvelteAttribute"
+  ) {
+    const typing = buildAttributeType(
+      attributeParent.parent,
+      attribute.key.name,
+      ctx,
+    );
+    const mustache = convertMustacheTag(nodes[0], attribute, typing, ctx);
+    attribute.value.push(mustache);
+    return;
+  }
+  for (const v of nodes) {
+    if (v.type === "Text") {
       attribute.value.push(convertTextToLiteral(v, attribute, ctx));
       continue;
     }
     if (v.type === "MustacheTag") {
-      const mustache = convertMustacheTag(v, attribute, ctx);
+      const mustache = convertMustacheTag(v, attribute, null, ctx);
       attribute.value.push(mustache);
       continue;
     }
@@ -246,6 +272,47 @@ function processAttributeValue(
   }
 }
 
+/** Build attribute type */
+function buildAttributeType(
+  element: SvelteElement | SvelteScriptElement | SvelteStyleElement,
+  attrName: string,
+  ctx: Context,
+) {
+  if (
+    svelteVersion.gte(5) &&
+    attrName.startsWith("on") &&
+    (element.type !== "SvelteElement" || element.kind === "html")
+  ) {
+    return buildEventHandlerType(element, attrName.slice(2), ctx);
+  }
+  if (element.type !== "SvelteElement" || element.kind !== "component") {
+    return null;
+  }
+  const elementName = ctx.elements.get(element)!.name;
+  const componentPropsType = `import('svelte').ComponentProps<${elementName}>`;
+  return conditional({
+    check: `'${attrName}'`,
+    extends: `infer PROP`,
+    true: conditional({
+      check: `PROP`,
+      extends: `keyof ${componentPropsType}`,
+      true: `${componentPropsType}[PROP]`,
+      false: `never`,
+    }),
+    false: `never`,
+  });
+
+  /** Generate `C extends E ? T : F` type. */
+  function conditional(types: {
+    check: string;
+    extends: string;
+    true: string;
+    false: string;
+  }) {
+    return `${types.check} extends ${types.extends}?(${types.true}):(${types.false})`;
+  }
+}
+
 /** Convert for Spread */
 function convertSpreadAttribute(
   node: SvAST.Spread,
@@ -491,7 +558,7 @@ function convertStyleDirective(
     end: keyName.range[1],
   });
 
-  processAttributeValue(node.value, directive, ctx);
+  processAttributeValue(node.value, directive, parent, ctx);
 
   return directive;
 }

Diff for: src/parser/converts/element.ts

@@ -117,7 +117,7 @@ export function* convertChildren(
       continue;
     }
     if (child.type === "MustacheTag") {
-      yield convertMustacheTag(child, parent, ctx);
+      yield convertMustacheTag(child, parent, null, ctx);
       continue;
     }
     if (child.type === "RawMustacheTag") {

Diff for: src/parser/converts/mustache.ts

@@ -10,9 +10,10 @@ import type * as SvAST from "../svelte-ast-types";
 export function convertMustacheTag(
   node: SvAST.MustacheTag,
   parent: SvelteMustacheTag["parent"],
+  typing: string | null,
   ctx: Context,
 ): SvelteMustacheTagText {
-  return convertMustacheTag0(node, "text", parent, ctx);
+  return convertMustacheTag0(node, "text", parent, typing, ctx);
 }
 /** Convert for MustacheTag */
 export function convertRawMustacheTag(
@@ -24,6 +25,7 @@ export function convertRawMustacheTag(
     node,
     "raw",
     parent,
+    null,
     ctx,
   );
   const atHtmlStart = ctx.code.indexOf("@html", mustache.range[0]);
@@ -64,6 +66,7 @@ function convertMustacheTag0<T extends SvelteMustacheTag>(
   node: SvAST.MustacheTag | SvAST.RawMustacheTag,
   kind: T["kind"],
   parent: T["parent"],
+  typing: string | null,
   ctx: Context,
 ): T {
   const mustache = {
@@ -73,7 +76,7 @@ function convertMustacheTag0<T extends SvelteMustacheTag>(
     parent,
     ...ctx.getConvertLocation(node),
   } as T;
-  ctx.scriptLet.addExpression(node.expression, mustache, null, (es) => {
+  ctx.scriptLet.addExpression(node.expression, mustache, typing, (es) => {
     mustache.expression = es;
   });
   return mustache;

Diff for: tests/fixtures/parser/ast/svelte5/ts-event01-input.svelte

@@ -0,0 +1,5 @@
+<script lang="ts">
+    import Component from 'foo.svelte'
+</script>
+<button onclick="{e=>{}}"></button>
+<Component onclick="{e=>{}}"></Component>

Diff for: tests/fixtures/parser/ast/svelte5/ts-event01-no-unused-vars-result.json

@@ -0,0 +1,14 @@
+[
+  {
+    "ruleId": "no-unused-vars",
+    "code": "e",
+    "line": 4,
+    "column": 19
+  },
+  {
+    "ruleId": "no-unused-vars",
+    "code": "e",
+    "line": 5,
+    "column": 22
+  }
+]