From f5d1bba7b33b697eeb73bd9de1c01320f3d43bab Mon Sep 17 00:00:00 2001
From: Eemeli Aro <eemeli@gmail.com>
Date: Tue, 14 Mar 2023 13:30:15 +0200
Subject: [PATCH 1/2] feat(mf2): Use column-first rather than first-match
 selection

---
 packages/mf2-icu-mf1/src/runtime.ts           | 10 ++--
 .../src/__fixtures/test-messages.json         |  2 +-
 .../src/message-value/message-fallback.ts     |  4 +-
 .../src/message-value/message-markup.ts       |  8 +--
 .../src/message-value/message-number.ts       |  9 +--
 .../src/message-value/message-value.ts        |  8 ++-
 .../src/message-value/resolved-message.ts     | 60 ++++++++++++++-----
 7 files changed, 69 insertions(+), 32 deletions(-)

diff --git a/packages/mf2-icu-mf1/src/runtime.ts b/packages/mf2-icu-mf1/src/runtime.ts
index 4e01ca46..38ef9784 100644
--- a/packages/mf2-icu-mf1/src/runtime.ts
+++ b/packages/mf2-icu-mf1/src/runtime.ts
@@ -104,17 +104,17 @@ class MessageMF1Number extends MessageNumber {
     super(locale, number, opt);
   }
 
-  matchSelectKey(key: string) {
+  selectKey(keys: Set<string>) {
     let num = this.value;
     const offset = getMF1Offset(this.options);
     if (offset) {
       if (typeof num === 'bigint') num += BigInt(offset);
       else num += offset;
     }
-    return (
-      (/^[0-9]+$/.test(key) && key === String(num)) ||
-      key === this.getPluralCategory()
-    );
+    const str = String(num);
+    if (keys.has(str)) return str;
+    const cat = this.getPluralCategory();
+    return keys.has(cat) ? cat : null;
   }
 }
 
diff --git a/packages/mf2-messageformat/src/__fixtures/test-messages.json b/packages/mf2-messageformat/src/__fixtures/test-messages.json
index aa858396..3191f862 100644
--- a/packages/mf2-messageformat/src/__fixtures/test-messages.json
+++ b/packages/mf2-messageformat/src/__fixtures/test-messages.json
@@ -123,7 +123,7 @@
   {
     "src": "match {$foo} when one {one} when 1 {=1} when * {other}",
     "params": { "foo": 1 },
-    "exp": "one"
+    "exp": "=1"
   },
   {
     "src": "match {$foo} {$bar} when one one {one one} when one * {one other} when * * {other}",
diff --git a/packages/mf2-messageformat/src/message-value/message-fallback.ts b/packages/mf2-messageformat/src/message-value/message-fallback.ts
index a5d20cf5..c831bf59 100644
--- a/packages/mf2-messageformat/src/message-value/message-fallback.ts
+++ b/packages/mf2-messageformat/src/message-value/message-fallback.ts
@@ -19,8 +19,8 @@ export class MessageFallback extends MessageValue<undefined> {
     super(FALLBACK, locale, undefined, fmt);
   }
 
-  matchSelectKey() {
-    return false;
+  selectKey() {
+    return null;
   }
 
   toString() {
diff --git a/packages/mf2-messageformat/src/message-value/message-markup.ts b/packages/mf2-messageformat/src/message-value/message-markup.ts
index 6f26d183..3c54f126 100644
--- a/packages/mf2-messageformat/src/message-value/message-markup.ts
+++ b/packages/mf2-messageformat/src/message-value/message-markup.ts
@@ -29,8 +29,8 @@ export class MessageMarkupStart extends MessageValue<string> {
     this.options = { ...options };
   }
 
-  matchSelectKey() {
-    return false;
+  selectKey() {
+    return null;
   }
 
   toString() {
@@ -52,8 +52,8 @@ export class MessageMarkupEnd extends MessageValue<string> {
     super(MARKUP_END, locale, name, options);
   }
 
-  matchSelectKey() {
-    return false;
+  selectKey() {
+    return null;
   }
 
   toString() {
diff --git a/packages/mf2-messageformat/src/message-value/message-number.ts b/packages/mf2-messageformat/src/message-value/message-number.ts
index 9c213063..19d3f915 100644
--- a/packages/mf2-messageformat/src/message-value/message-number.ts
+++ b/packages/mf2-messageformat/src/message-value/message-number.ts
@@ -66,10 +66,11 @@ export class MessageNumber extends MessageValue<number | bigint> {
    * For example, cardinal English plurals only use `one` and `other`,
    * so a key `zero` will never be matched for that locale.
    */
-  matchSelectKey(key: string) {
-    if (/^[0-9]+$/.test(key) && key === String(this.value)) return true;
-    if (key === this.getPluralCategory()) return { plural: key };
-    return false;
+  selectKey(keys: Set<string>) {
+    const str = String(this.value);
+    if (keys.has(str)) return str;
+    const cat = this.getPluralCategory();
+    return keys.has(cat) ? cat : null;
   }
 
   toParts(): Intl.NumberFormatPart[] {
diff --git a/packages/mf2-messageformat/src/message-value/message-value.ts b/packages/mf2-messageformat/src/message-value/message-value.ts
index 0712d077..c9db6301 100644
--- a/packages/mf2-messageformat/src/message-value/message-value.ts
+++ b/packages/mf2-messageformat/src/message-value/message-value.ts
@@ -79,8 +79,12 @@ export class MessageValue<T = unknown> {
     this.#localeContext = locale;
   }
 
-  matchSelectKey(key: string): boolean | Meta {
-    return this.value != null && String(this.value) === key;
+  selectKey(keys: Set<string>): string | null {
+    if (this.value != null) {
+      const str = String(this.value);
+      if (keys.has(str)) return str;
+    }
+    return null;
   }
 
   toString(onError?: Context['onError']): string {
diff --git a/packages/mf2-messageformat/src/message-value/resolved-message.ts b/packages/mf2-messageformat/src/message-value/resolved-message.ts
index e9d5a4d7..f709e223 100644
--- a/packages/mf2-messageformat/src/message-value/resolved-message.ts
+++ b/packages/mf2-messageformat/src/message-value/resolved-message.ts
@@ -14,22 +14,52 @@ function getPattern(
       return { pattern: message.pattern.body };
 
     case 'select': {
-      const resSelectors = message.selectors.map(sel => context.resolve(sel));
+      const ctx = message.selectors.map(sel => ({
+        selector: context.resolve(sel),
+        best: null as string | null,
+        keys: null as Set<string> | null
+      }));
 
-      cases: for (const { keys, value } of message.variants) {
-        let meta: Meta | undefined = undefined;
-        for (let i = 0; i < keys.length; ++i) {
-          const key = keys[i];
-          const rs = resSelectors[i];
-          const match = key.type === '*' || rs?.matchSelectKey(key.value);
-          if (!match) continue cases;
-          if (typeof match === 'object')
-            meta = Object.assign(meta ?? {}, match);
+      let candidates = message.variants;
+      loop: for (let i = 0; i < ctx.length; ++i) {
+        const sc = ctx[i];
+        if (!sc.keys) {
+          sc.keys = new Set();
+          for (const { keys } of candidates) {
+            const key = keys[i];
+            if (!key) break loop; // key-mismatch error
+            if (key.type !== '*') sc.keys.add(key.value);
+          }
+        }
+        sc.best = sc.keys.size ? sc.selector.selectKey(sc.keys) : null;
+
+        // Leave out all candidate variants that aren't the best,
+        // or only the catchall ones, if nothing else matches.
+        candidates = candidates.filter(v => {
+          const k = v.keys[i];
+          if (k.type === '*') return sc.best == null;
+          return sc.best === k.value;
+        });
+
+        // If we've run out of candidates,
+        // drop the previous best key of the preceding selector,
+        // reset all subsequent key sets,
+        // and restart the loop.
+        if (candidates.length === 0) {
+          if (i === 0) break; // No match; should not happen
+          const prev = ctx[i - 1];
+          if (prev.best == null) prev.keys?.clear();
+          else prev.keys?.delete(prev.best);
+          for (let j = i; j < ctx.length; ++j) ctx[j].keys = null;
+          candidates = message.variants;
+          i = -1;
         }
-        return { pattern: value.body, meta };
       }
 
-      return { pattern: [], meta: { selectResult: 'no-match' } };
+      const res = candidates[0];
+      return res
+        ? { pattern: res.value.body }
+        : { pattern: [], meta: { selectResult: 'no-match' } };
     }
 
     default:
@@ -52,8 +82,10 @@ export class ResolvedMessage extends MessageValue<MessageValue[]> {
     super(MESSAGE, context, resMsg, { meta, source });
   }
 
-  matchSelectKey(key: string) {
-    return this.toString() === key;
+  selectKey(keys: Set<string>) {
+    let hasError = false;
+    const str = this.toString(() => (hasError = true));
+    return !hasError && keys.has(str) ? str : null;
   }
 
   toString(onError?: Context['onError']) {

From 102121b0bb765f8d11ca4035331bf6ba6585c19d Mon Sep 17 00:00:00 2001
From: Eemeli Aro <eemeli@gmail.com>
Date: Tue, 14 Mar 2023 15:03:26 +0200
Subject: [PATCH 2/2] chore: Publish

- messageformat@4.0.0-3.cf
---
 package-lock.json                       | 2 +-
 packages/mf2-messageformat/CHANGELOG.md | 4 ++++
 packages/mf2-messageformat/package.json | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index a79784ca..0e274f03 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12322,7 +12322,7 @@
     },
     "packages/mf2-messageformat": {
       "name": "messageformat",
-      "version": "4.0.0-3",
+      "version": "4.0.0-3.cf",
       "license": "Apache-2.0"
     },
     "packages/mf2-xliff": {
diff --git a/packages/mf2-messageformat/CHANGELOG.md b/packages/mf2-messageformat/CHANGELOG.md
index 2ad9f1f5..d4b6318f 100644
--- a/packages/mf2-messageformat/CHANGELOG.md
+++ b/packages/mf2-messageformat/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## [4.0.0-3.cf](https://github.com/messageformat/messageformat/compare/messageformat@4.0.0-3...messageformat@4.0.0-3.cf) (2023-03-14)
+
+* Use column-first rather than first-match selection ([f5d1bba](https://github.com/messageformat/messageformat/commit/f5d1bba7b33b697eeb73bd9de1c01320f3d43bab))
+
 ## [4.0.0-3](https://github.com/messageformat/messageformat/compare/messageformat@4.0.0-2...messageformat@4.0.0-3) (2023-03-14)
 
 * Use `|` rather than `()` as literal quotes ([15e1fcd](https://github.com/messageformat/messageformat/commit/15e1fcd65341a5ab536a06d4401b7f488b8cdfcc))
diff --git a/packages/mf2-messageformat/package.json b/packages/mf2-messageformat/package.json
index 809063ab..8f79c0b0 100644
--- a/packages/mf2-messageformat/package.json
+++ b/packages/mf2-messageformat/package.json
@@ -1,6 +1,6 @@
 {
   "name": "messageformat",
-  "version": "4.0.0-3",
+  "version": "4.0.0-3.cf",
   "description": "Intl.MessageFormat / Unicode MessageFormat 2 parser, runtime and polyfill",
   "keywords": [
     "messageformat",