[Fix] Merge queue rejects legitimate source changes

src/scripts/__tests__/coverage-contract.spec.mjs

@@ -0,0 +1,138 @@
+import { describe, expect, it } from "vitest"
+
+import { mergeCoverageSources, parseCoverageSourceLines } from "../coverage-contract.mjs"
+
+const coverage = (records) =>
+	records
+		.map(
+			([source, lines]) =>
+				`SF:${source}\n${lines.map((line) => `DA:${line},1`).join("\n")}\nLF:${lines.length}\nend_of_record`,
+		)
+		.join("\n")
+
+const parse = (records, lane) => parseCoverageSourceLines(coverage(records), lane)
+
+describe("coverage source equivalence", () => {
+	it("accepts legitimate changes to the instrumented source population", () => {
+		const before = [
+			["src/a.ts", [1]],
+			["src/b.ts", [1]],
+		]
+		const after = [
+			["src/a.ts", [1, 2]],
+			["src/b.ts", [1]],
+		]
+
+		expect(() =>
+			mergeCoverageSources(
+				["api", "core"],
+				[
+					["api", parse(after, "api")],
+					["core", parse([["src/a.ts", [1, 2]]], "core")],
+				],
+			),
+		).not.toThrow()
+		expect([...parse(after, "api").values()].reduce((sum, lines) => sum + lines.size, 0)).toBe(
+			[...parse(before, "api").values()].reduce((sum, lines) => sum + lines.size, 0) + 1,
+		)
+	})
+
+	it("rejects omitted lane coverage", () => {
+		expect(() => mergeCoverageSources(["api", "core"], [["api", parse([["src/a.ts", [1]]], "api")]])).toThrow(
+			"Coverage lane is missing: core",
+		)
+	})
+
+	it("rejects duplicated lane coverage", () => {
+		expect(() =>
+			mergeCoverageSources(
+				["api"],
+				[
+					["api", parse([["src/a.ts", [1]]], "api")],
+					["api", parse([["src/a.ts", [1]]], "api")],
+				],
+			),
+		).toThrow("Coverage lane is duplicated: api")
+	})
+
+	it("rejects duplicate source records within a lane", () => {
+		expect(() =>
+			parse(
+				[
+					["src/a.ts", [1]],
+					["src/a.ts", [1]],
+				],
+				"api",
+			),
+		).toThrow("api coverage contains duplicate source record: src/a.ts")
+	})
+
+	it("rejects unfinished source records", () => {
+		expect(() => parseCoverageSourceLines("SF:src/a.ts\nDA:1,1\nSF:src/b.ts\nLF:1", "api")).toThrow(
+			"api coverage contains an unfinished source record: src/a.ts",
+		)
+		expect(() => parseCoverageSourceLines("SF:src/a.ts\nDA:1,1\n", "api")).toThrow(
+			"api coverage contains an unfinished source record: src/a.ts",
+		)
+		expect(() => parseCoverageSourceLines("SF:src/a.ts\nDA:1,1\nLF:1\n", "api")).toThrow(
+			"api coverage contains an unfinished source record: src/a.ts",
+		)
+	})
+
+	it.each([
+		["empty source paths", "SF:\nLF:0\nend_of_record", "empty source path"],
+		["DA outside a record", "DA:1,1", "DA outside a source record"],
+		["LF outside a record", "LF:0", "LF outside a source record"],
+		["DA after LF", "SF:src/a.ts\nDA:1,1\nLF:1\nDA:2,1\nend_of_record", "DA after LF"],
+		["missing DA counts", "SF:src/a.ts\nDA:1\nLF:1\nend_of_record", "invalid DA"],
+		["nonnumeric DA counts", "SF:src/a.ts\nDA:1,nope\nLF:1\nend_of_record", "invalid DA"],
+		[
+			"unsafe DA line numbers",
+			`SF:src/a.ts\nDA:${Number.MAX_SAFE_INTEGER + 1},0\nLF:1\nend_of_record`,
+			"invalid DA",
+		],
+		["unsafe DA counts", `SF:src/a.ts\nDA:1,${Number.MAX_SAFE_INTEGER + 1}\nLF:1\nend_of_record`, "invalid DA"],
+		["duplicate DA lines", "SF:src/a.ts\nDA:1,0\nDA:1,1\nLF:2\nend_of_record", "duplicate DA"],
+		["empty LF values", "SF:src/a.ts\nLF:\nend_of_record", "invalid LF"],
+		["nonnumeric LF values", "SF:src/a.ts\nLF:nope\nend_of_record", "invalid LF"],
+		["invalid terminators", "end_of_record", "invalid record terminator"],
+	])("rejects %s", (_name, lcov, error) => {
+		expect(() => parseCoverageSourceLines(lcov, "api")).toThrow(error)
+	})
+
+	it("accepts DA and LF numeric boundaries", () => {
+		expect(() =>
+			parseCoverageSourceLines(
+				`SF:src/a.ts\nDA:1,0\nDA:${Number.MAX_SAFE_INTEGER},0,checksum\nLF:2\nend_of_record`,
+				"api",
+			),
+		).not.toThrow()
+	})
+
+	it("rejects empty and unexpected lane coverage", () => {
+		expect(() => mergeCoverageSources(["api"], [["api", new Map()]])).toThrow(
+			"Coverage lane has no instrumented lines: api",
+		)
+		expect(() =>
+			mergeCoverageSources(
+				["api"],
+				[
+					["api", parse([["src/a.ts", [1]]], "api")],
+					["core", parse([["src/a.ts", [1]]], "core")],
+				],
+			),
+		).toThrow("Unexpected coverage lane: core")
+	})
+
+	it("rejects conflicting instrumented line counts", () => {
+		expect(() =>
+			mergeCoverageSources(
+				["api", "core"],
+				[
+					["api", parse([["src/a.ts", [1, 3]]], "api")],
+					["core", parse([["src/a.ts", [1, 2]]], "core")],
+				],
+			),
+		).toThrow("core coverage has conflicting instrumented lines for src/a.ts")
+	})
+})

src/scripts/coverage-contract.mjs

@@ -0,0 +1,70 @@
+export const parseCoverageSourceLines = (lcov, lane) => {
+	const sources = new Map()
+	let source
+	let instrumentedLines = new Set()
+	let hasSummary = false
+
+	for (const line of lcov.split(/\r?\n/)) {
+		if (line.startsWith("SF:")) {
+			if (source) throw new Error(`${lane} coverage contains an unfinished source record: ${source}`)
+			source = line.slice(3)
+			if (!source) throw new Error(`${lane} coverage contains an empty source path`)
+			instrumentedLines = new Set()
+			hasSummary = false
+		} else if (line.startsWith("DA:")) {
+			if (!source) throw new Error(`${lane} coverage contains DA outside a source record`)
+			if (hasSummary) throw new Error(`${lane} coverage contains DA after LF for ${source}`)
+			const match = /^DA:(\d+),(\d+)(?:,[^,\r\n]+)?$/.exec(line)
+			const lineNumber = match ? Number(match[1]) : Number.NaN
+			const executionCount = match ? Number(match[2]) : Number.NaN
+			if (!Number.isSafeInteger(lineNumber) || lineNumber < 1)
+				throw new Error(`${lane} coverage contains invalid DA for ${source}`)
+			if (!Number.isSafeInteger(executionCount))
+				throw new Error(`${lane} coverage contains invalid DA for ${source}`)
+			if (instrumentedLines.has(lineNumber))
+				throw new Error(`${lane} coverage contains duplicate DA for ${source}:${lineNumber}`)
+			instrumentedLines.add(lineNumber)
+		} else if (line.startsWith("LF:")) {
+			if (!source) throw new Error(`${lane} coverage contains LF outside a source record`)
+			if (sources.has(source)) throw new Error(`${lane} coverage contains duplicate source record: ${source}`)
+
+			const match = /^LF:(\d+)$/.exec(line)
+			const linesFound = match ? Number(match[1]) : Number.NaN
+			if (!Number.isSafeInteger(linesFound) || linesFound < 0 || linesFound !== instrumentedLines.size)
+				throw new Error(`${lane} coverage contains invalid LF for ${source}`)
+			sources.set(source, instrumentedLines)
+			hasSummary = true
+		} else if (line === "end_of_record") {
+			if (!source || !hasSummary) throw new Error(`${lane} coverage contains an invalid record terminator`)
+			source = undefined
+		}
+	}
+	if (source) throw new Error(`${lane} coverage contains an unfinished source record: ${source}`)
+
+	return sources
+}
+
+export const mergeCoverageSources = (expectedLanes, coverageByLane) => {
+	const lanes = new Set()
+	const combinedSources = new Map()
+	for (const [lane, sources] of coverageByLane) {
+		if (lanes.has(lane)) throw new Error(`Coverage lane is duplicated: ${lane}`)
+		lanes.add(lane)
+		if (sources.size === 0 || [...sources.values()].every((lines) => lines.size === 0))
+			throw new Error(`Coverage lane has no instrumented lines: ${lane}`)
+		for (const [source, instrumentedLines] of sources) {
+			const existingLines = combinedSources.get(source)
+			if (
+				existingLines &&
+				(existingLines.size !== instrumentedLines.size ||
+					[...existingLines].some((line) => !instrumentedLines.has(line)))
+			)
+				throw new Error(`${lane} coverage has conflicting instrumented lines for ${source}`)
+			combinedSources.set(source, instrumentedLines)
+		}
+	}
+
+	for (const lane of expectedLanes) if (!lanes.has(lane)) throw new Error(`Coverage lane is missing: ${lane}`)
+	for (const lane of lanes) if (!expectedLanes.includes(lane)) throw new Error(`Unexpected coverage lane: ${lane}`)
+	return combinedSources
+}

src/scripts/verify-coverage-contract.mjs

@@ -5,6 +5,8 @@
 import process from "node:process"
 import { promisify } from "node:util"
 
+import { mergeCoverageSources, parseCoverageSourceLines } from "./coverage-contract.mjs"
+
 const pnpm = process.platform === "win32" ? process.env.npm_execpath : "pnpm"
 if (!pnpm) throw new Error("pnpm executable path is unavailable")
 const command = process.platform === "win32" ? process.execPath : pnpm
@@ -151,16 +153,9 @@
 	rmSync(collectionDirectory, { recursive: true, force: true })
 }
 
-const coverageSources = new Map()
-for (const lane of [...ownershipLanes, "tree-sitter"]) {
-	let source
-	for (const line of readFileSync(resolve(root, "coverage", lane, "lcov.info"), "utf8").split(/\r?\n/)) {
-		if (line.startsWith("SF:")) source = line.slice(3)
-		if (line.startsWith("LF:")) coverageSources.set(source, Number(line.slice(3)))
-	}
-}
-const instrumentedLines = [...coverageSources.values()].reduce((sum, lines) => sum + lines, 0)
-if (coverageSources.size !== 469 || instrumentedLines !== 30_229)
-	throw new Error(
-		`Coverage source population changed: ${coverageSources.size} records and ${instrumentedLines} lines; verify equivalence and update the baseline deliberately`,
-	)
+const coverageLanes = [...ownershipLanes, "tree-sitter"]
+const coverageByLane = coverageLanes.map((lane) => [
+	lane,
+	parseCoverageSourceLines(readFileSync(resolve(root, "coverage", lane, "lcov.info"), "utf8"), lane),
+])
+mergeCoverageSources(coverageLanes, coverageByLane)