Merge pull request #174 from backstage/rugvip/higher

pr-automation: tweak priority caluclation to taper off more slowy with size + add config

Author: Rugvip

pr-automation/action.yml

@@ -34,6 +34,26 @@ inputs:
   actor:
     description: Override for the actor (user who triggered the event)
     required: false
+  priority-base:
+    description: Starting priority value before size-based reduction
+    required: false
+    default: "100"
+  priority-exponent-base:
+    description: Base of the exponential decay (0.5 = halve priority per divisor)
+    required: false
+    default: "0.5"
+  priority-exponent-offset:
+    description: Lines of additions before priority starts decreasing
+    required: false
+    default: "0"
+  priority-exponent-divisor:
+    description: Lines of additions per halving of priority
+    required: false
+    default: "500"
+  priority-reviewer-bump:
+    description: Priority boost when PR has reviewer-approved label
+    required: false
+    default: "100"
 outputs: {}
 runs:
   using: node24

pr-automation/getConfig.ts

@@ -36,13 +36,14 @@ export function getConfig(): Config {
     statusFieldName: 'Status',
     priorityFieldName: 'Priority',
     priorityParams: {
-      base: 100,
-      exponentBase: 0.5,
-      exponentOffset: 1,
-      exponentDivisor: 99,
-      min: 0,
-      max: 100,
-      reviewerBump: 100,
+      base: parseNumber(core.getInput('priority-base'), 100),
+      exponentBase: parseNumber(core.getInput('priority-exponent-base'), 0.5),
+      exponentOffset: parseNumber(core.getInput('priority-exponent-offset'), 0),
+      exponentDivisor: parseNumber(
+        core.getInput('priority-exponent-divisor'),
+        500,
+      ),
+      reviewerBump: parseNumber(core.getInput('priority-reviewer-bump'), 100),
     },
   };
 }

pr-automation/logic/calculatePriority.test.ts

@@ -1,41 +1,32 @@
 import { calculatePriority } from './calculatePriority';
 
 describe('calculatePriority', () => {
+  // 0 lines → 100, 500 lines → ~50, 5000 lines → 0
   const defaultParams = {
     base: 100,
     exponentBase: 0.5,
-    exponentOffset: 1,
-    exponentDivisor: 99,
-    min: 0,
-    max: 100,
+    exponentOffset: 0,
+    exponentDivisor: 500,
     reviewerBump: 100,
   };
 
-  it('calculates priority within bounds and adds reviewer bump', () => {
-    const priorityWithoutBump = calculatePriority(5, defaultParams, false);
-    const priorityWithBump = calculatePriority(5, defaultParams, true);
+  it('calculates expected priority values based on PR size', () => {
+    expect(calculatePriority(0, defaultParams, false)).toBe(100);
+    expect(calculatePriority(500, defaultParams, false)).toBe(50);
+    expect(calculatePriority(5000, defaultParams, false)).toBe(0);
+  });
+
+  it('adds reviewer bump to priority', () => {
+    const priorityWithoutBump = calculatePriority(500, defaultParams, false);
+    const priorityWithBump = calculatePriority(500, defaultParams, true);
 
-    expect(priorityWithoutBump).toBeGreaterThanOrEqual(0);
-    expect(priorityWithoutBump).toBeLessThanOrEqual(100);
     expect(priorityWithBump).toBe(priorityWithoutBump + 100);
-    expect(priorityWithBump).toBeGreaterThanOrEqual(100);
   });
 
-  it('respects min and max bounds and handles edge cases', () => {
-    const paramsWithTightBounds = {
-      ...defaultParams,
-      min: 10,
-      max: 50,
-    };
-    const priorityHigh = calculatePriority(1000, paramsWithTightBounds, false);
-    const priorityZero = calculatePriority(0, defaultParams, false);
-    const priorityVeryHigh = calculatePriority(100000, defaultParams, false);
+  it('clamps priority between 0 and base', () => {
+    const paramsWithLowBase = { ...defaultParams, base: 50 };
 
-    expect(priorityHigh).toBeGreaterThanOrEqual(10);
-    expect(priorityHigh).toBeLessThanOrEqual(50);
-    expect(priorityZero).toBeGreaterThanOrEqual(0);
-    expect(priorityZero).toBeLessThanOrEqual(100);
-    expect(priorityVeryHigh).toBeGreaterThanOrEqual(0);
-    expect(priorityVeryHigh).toBeLessThanOrEqual(100);
+    expect(calculatePriority(0, paramsWithLowBase, false)).toBe(50);
+    expect(calculatePriority(5000, paramsWithLowBase, false)).toBe(0);
   });
 });

pr-automation/logic/calculatePriority.ts

@@ -12,7 +12,7 @@ export function calculatePriority(
       (additions - params.exponentOffset) / params.exponentDivisor,
     );
   let priority = Math.round(rawPriority);
-  priority = Math.max(params.min, Math.min(params.max, priority));
+  priority = Math.max(0, Math.min(params.base, priority));
 
   if (hasReviewerApproved) {
     priority += params.reviewerBump;

pr-automation/types.ts

@@ -102,18 +102,14 @@ export interface SizeLabelConfig {
 }
 
 export interface PriorityParams {
-  /** Starting priority value before size-based reduction */
+  /** Starting/max priority value before size-based reduction (min is always 0) */
   base: number;
-  /** Base of the exponential decay (e.g., 0.5 = halve priority) */
+  /** Base of the exponential decay (e.g., 0.5 = halve priority per divisor) */
   exponentBase: number;
   /** Lines of additions before priority starts decreasing */
   exponentOffset: number;
-  /** Lines of additions per halving of priority (when exponentBase is 0.5) */
+  /** Lines of additions per halving of priority (default 500: 0→100, 500→50, 5000→0) */
   exponentDivisor: number;
-  /** Minimum allowed priority value */
-  min: number;
-  /** Maximum allowed priority value */
-  max: number;
   /** Priority boost when PR has reviewer-approved label */
   reviewerBump: number;
 }