feat: celebrate bundle size decreases and report no-change

README.md

@@ -37,21 +37,21 @@ jobs:
 
 ## Inputs
 
-| Name                   | Description                                                                    | Required | Default                                   |
-| ---------------------- | ------------------------------------------------------------------------------ | -------- | ----------------------------------------- |
-| `base-ref`             | Base ref to compare against (defaults to main or PR target)                    | No       | Auto-detected from PR or `main`           |
-| `github-token`         | The GitHub token for authentication                                            | Yes      | `${{ github.token }}`                     |
-| `pr-number`            | The number of the pull request to comment on                                   | Yes      | `${{ github.event.pull_request.number }}` |
-| `dependency-threshold` | Threshold for warning about significant increase in number of dependencies     | No       | `10`                                      |
-| `size-threshold`       | Threshold (in bytes) for warning about significant increase in package size    | No       | `100000`                                  |
-| `duplicate-threshold`  | Threshold for warning about packages with multiple versions                    | No       | `1`                                       |
-| `base-packages`        | Glob pattern for base branch pack files (e.g., `"./base-packs/*.tgz"`)         | No       | None                                      |
-| `source-packages`      | Glob pattern for source branch pack files (e.g., `"./source-packs/*.tgz"`)     | No       | None                                      |
-| `pack-size-threshold`  | Threshold (in bytes) for warning about significant increase in total pack size | No       | `50000`                                   |
-| `detect-replacements`  | Detect modules which have community suggested alternatives                     | No       | `true`                                    |
-| `working-directory`    | Working directory to scan for package lock file                                | No       | None                                      |
-| `mode`                 | Run mode: `comment`, `artifact`, or `comment-from-artifact`                    | No       | `comment`                                 |
-| `artifact-path`        | Path to the artifact JSON file (for `comment-from-artifact` mode)              | No       | None                                      |
+| Name                   | Description                                                                                                                | Required | Default                                   |
+| ---------------------- | -------------------------------------------------------------------------------------------------------------------------- | -------- | ----------------------------------------- |
+| `base-ref`             | Base ref to compare against (defaults to main or PR target)                                                                | No       | Auto-detected from PR or `main`           |
+| `github-token`         | The GitHub token for authentication                                                                                        | Yes      | `${{ github.token }}`                     |
+| `pr-number`            | The number of the pull request to comment on                                                                               | Yes      | `${{ github.event.pull_request.number }}` |
+| `dependency-threshold` | Threshold for warning about significant increase in number of dependencies                                                 | No       | `10`                                      |
+| `size-threshold`       | Threshold (in bytes) for warning about significant increase in package size                                                | No       | `100000`                                  |
+| `duplicate-threshold`  | Threshold for warning about packages with multiple versions                                                                | No       | `1`                                       |
+| `base-packages`        | Glob pattern for base branch pack files (e.g., `"./base-packs/*.tgz"`)                                                     | No       | None                                      |
+| `source-packages`      | Glob pattern for source branch pack files (e.g., `"./source-packs/*.tgz"`)                                                 | No       | None                                      |
+| `pack-size-threshold`  | Threshold (in bytes) for warning about significant increase in total pack size. Set to `-1` to always report size changes. | No       | `50000`                                   |
+| `detect-replacements`  | Detect modules which have community suggested alternatives                                                                 | No       | `true`                                    |
+| `working-directory`    | Working directory to scan for package lock file                                                                            | No       | None                                      |
+| `mode`                 | Run mode: `comment`, `artifact`, or `comment-from-artifact`                                                                | No       | `comment`                                 |
+| `artifact-path`        | Path to the artifact JSON file (for `comment-from-artifact` mode)                                                          | No       | None                                      |
 
 ## Example with custom inputs
 
@@ -93,11 +93,23 @@ The action accepts glob patterns to locate package tarballs for comparison:
 
 - **`base-packages`** - Glob pattern for base branch pack files (e.g., `"./base-packs/*.tgz"`)
 - **`source-packages`** - Glob pattern for source branch pack files (e.g., `"./source-packs/*.tgz"`)
-- **`pack-size-threshold`** - Threshold in bytes for warning about significant pack size increases
 
 > [!NOTE]
 > Package bundle analysis only runs when both `base-packages` and `source-packages` are provided. If these inputs are not set, this feature is skipped entirely.
 
+### Always Report Bundle Size Changes
+
+To always report bundle size changes, set `pack-size-threshold` to `-1`. This will display bundle size differences even if they are reductions, giving you full visibility into how your changes affect the published package size.
+
+```yaml
+- name: Create Diff
+  uses: e18e/action-dependency-diff@v1
+  with:
+    base-packages: './base-packs/*.tgz'
+    source-packages: './source-packs/*.tgz'
+    pack-size-threshold: -1
+```
+
 You can see an example of how to set this up in the [bundle difference workflow](./recipes/bundle-diff.yml).
 
 ## Module Replacements

action.yml

@@ -33,7 +33,7 @@ inputs:
     description: 'Glob pattern for source branch pack files (e.g., "./source-packs/*.tgz")'
     required: false
   pack-size-threshold:
-    description: 'Threshold (in bytes) for warning about significant increase in total pack size'
+    description: 'Threshold (in bytes) for warning about significant increase in total pack size. Set to -1 to always report size changes.'
     required: false
     default: '50000'
   duplicate-threshold:

build/main.js

@@ -24393,7 +24393,7 @@ function comparePackSizes(basePacks, sourcePacks, threshold) {
     const baseSize = basePack?.size ?? null;
     const sourceSize = sourcePack?.size ?? null;
     const sizeChange = (sourceSize ?? 0) - (baseSize ?? 0);
-    const exceedsThreshold = sizeChange >= threshold;
+    const exceedsThreshold = threshold === -1 ? sizeChange !== 0 : sizeChange >= threshold;
     packChanges.push({
       name: packName,
       baseSize,
@@ -24815,26 +24815,39 @@ ${provenanceRows.join("\n")}`
 }
 
 // src/checks/bundle-size.ts
+function formatBytesSigned(bytes) {
+  return `${bytes > 0 ? "+" : ""}${formatBytes(bytes)}`;
+}
 async function scanForBundleSize(messages, basePacks, sourcePacks, threshold) {
   if (basePacks.length === 0 && sourcePacks.length === 0) {
     return;
   }
   const comparison = comparePackSizes(basePacks, sourcePacks, threshold);
   const packWarnings = comparison.packChanges.filter(
-    (change) => change.exceedsThreshold && change.sizeChange > 0
+    (change) => change.exceedsThreshold
   );
+  if (threshold === -1 && packWarnings.length === 0) {
+    messages.push(`## \u{1F4E6} Package Bundle Size
+
+No bundle size changes.`);
+    return;
+  }
   if (packWarnings.length > 0) {
+    const hasDecreases = packWarnings.some((c) => c.sizeChange < 0);
+    const hasIncreases = packWarnings.some((c) => c.sizeChange > 0);
+    const heading = hasDecreases && hasIncreases ? "## \u{1F4E6} Package Bundle Size Changes" : hasDecreases ? "## \u{1F389} Package Size Decrease" : "## \u26A0\uFE0F Package Size Increase";
     const packRows = packWarnings.map((change) => {
       const baseSize = change.baseSize ? formatBytes(change.baseSize) : "New";
       const sourceSize = change.sourceSize ? formatBytes(change.sourceSize) : "Removed";
-      const sizeChange = formatBytes(change.sizeChange);
+      const sizeChange = formatBytesSigned(change.sizeChange);
       return `| ${change.name} | ${baseSize} | ${sourceSize} | ${sizeChange} |`;
     }).join("\n");
+    const thresholdText = threshold === -1 ? "" : `
+These packages exceed the size change threshold of ${formatBytes(threshold)}:
+`;
     messages.push(
-      `## \u26A0\uFE0F Package Size Increase
-
-These packages exceed the size increase threshold of ${formatBytes(threshold)}:
-
+      `${heading}
+${thresholdText}
 | \u{1F4E6} Package | \u{1F4CF} Base Size | \u{1F4CF} Source Size | \u{1F4C8} Size Change |
 | --- | --- | --- | --- |
 ${packRows}`
@@ -24984,7 +24997,9 @@ async function analyzeAndComment() {
       `Parsed current lockfile with ${parsedCurrentLock.packages.length} packages`
     );
   } catch (err) {
-    throw new Error(`Failed to parse current lockfile: ${err}`);
+    throw new Error(`Failed to parse current lockfile: ${err}`, {
+      cause: err
+    });
   }
   try {
     parsedBaseLock = await parse2(
@@ -24996,7 +25011,9 @@ async function analyzeAndComment() {
       `Parsed base lockfile with ${parsedBaseLock.packages.length} packages`
     );
   } catch (err) {
-    throw new Error(`Failed to parse base lockfile: ${err}`);
+    throw new Error(`Failed to parse base lockfile: ${err}`, {
+      cause: err
+    });
   }
   const currentDeps = computeDependencyVersions(parsedCurrentLock);
   const baseDeps = computeDependencyVersions(parsedBaseLock);

src/checks/bundle-size.ts

@@ -1,6 +1,10 @@
 import {formatBytes} from '../common.js';
 import {comparePackSizes, type PackInfo} from '../packs.js';
 
+function formatBytesSigned(bytes: number): string {
+  return `${bytes > 0 ? '+' : ''}${formatBytes(bytes)}`;
+}
+
 export async function scanForBundleSize(
   messages: string[],
   basePacks: PackInfo[],
@@ -11,27 +15,44 @@ export async function scanForBundleSize(
     return;
   }
   const comparison = comparePackSizes(basePacks, sourcePacks, threshold);
+
   const packWarnings = comparison.packChanges.filter(
-    (change) => change.exceedsThreshold && change.sizeChange > 0
+    (change) => change.exceedsThreshold
   );
 
+  if (threshold === -1 && packWarnings.length === 0) {
+    messages.push(`## 📦 Package Bundle Size\n\nNo bundle size changes.`);
+    return;
+  }
+
   if (packWarnings.length > 0) {
+    const hasDecreases = packWarnings.some((c) => c.sizeChange < 0);
+    const hasIncreases = packWarnings.some((c) => c.sizeChange > 0);
+    const heading =
+      hasDecreases && hasIncreases
+        ? '## 📦 Package Bundle Size Changes'
+        : hasDecreases
+          ? '## 🎉 Package Size Decrease'
+          : '## ⚠️ Package Size Increase';
     const packRows = packWarnings
       .map((change) => {
         const baseSize = change.baseSize ? formatBytes(change.baseSize) : 'New';
         const sourceSize = change.sourceSize
           ? formatBytes(change.sourceSize)
           : 'Removed';
-        const sizeChange = formatBytes(change.sizeChange);
+        const sizeChange = formatBytesSigned(change.sizeChange);
         return `| ${change.name} | ${baseSize} | ${sourceSize} | ${sizeChange} |`;
       })
       .join('\n');
 
-    messages.push(
-      `## ⚠️ Package Size Increase
-
-These packages exceed the size increase threshold of ${formatBytes(threshold)}:
+    const thresholdText =
+      threshold === -1
+        ? ''
+        : `\nThese packages exceed the size change threshold of ${formatBytes(threshold)}:\n`;
 
+    messages.push(
+      `${heading}
+${thresholdText}
 | 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
 | --- | --- | --- | --- |
 ${packRows}`

src/packs.ts

@@ -175,7 +175,8 @@ export function comparePackSizes(
     const sourceSize = sourcePack?.size ?? null;
 
     const sizeChange = (sourceSize ?? 0) - (baseSize ?? 0);
-    const exceedsThreshold = sizeChange >= threshold;
+    const exceedsThreshold =
+      threshold === -1 ? sizeChange !== 0 : sizeChange >= threshold;
 
     packChanges.push({
       name: packName,

test/checks/__snapshots__/bundle-size_test.ts.snap

@@ -0,0 +1,84 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`scanForBundleSize > should report no bundle size change with threshold=-1 when diff is 0 1`] = `
+[
+  "## 📦 Package Bundle Size
+
+No bundle size changes.",
+]
+`;
+
+exports[`scanForBundleSize > should report size decrease when threshold is -1 1`] = `
+[
+  "## 🎉 Package Size Decrease
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| my-package | 200 kB | 100 kB | -100 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should show both decreases and increases when threshold is -1 1`] = `
+[
+  "## 📦 Package Bundle Size Changes
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| pkg-b | 50 kB | 150 kB | +100 kB |
+| pkg-a | 200 kB | 100 kB | -100 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should show new packages when threshold is -1 1`] = `
+[
+  "## ⚠️ Package Size Increase
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| new-package | New | 50 kB | +50 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should show only increases when threshold is -1 and no decreases 1`] = `
+[
+  "## ⚠️ Package Size Increase
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| my-package | 100 kB | 200 kB | +100 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should show removed packages when threshold is -1 1`] = `
+[
+  "## 🎉 Package Size Decrease
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| old-package | 50 kB | Removed | -50 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should warn about an increase regardless of other packages decreasing 1`] = `
+[
+  "## ⚠️ Package Size Increase
+
+These packages exceed the size change threshold of 50 kB:
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| pkg-b | 50 kB | 150 kB | +100 kB |",
+]
+`;
+
+exports[`scanForBundleSize > should warn about size increase exceeding threshold 1`] = `
+[
+  "## ⚠️ Package Size Increase
+
+These packages exceed the size change threshold of 50 kB:
+
+| 📦 Package | 📏 Base Size | 📏 Source Size | 📈 Size Change |
+| --- | --- | --- | --- |
+| my-package | 100 kB | 200 kB | +100 kB |",
+]
+`;