hardhat-slang: add initial support for the new slang compiler on a similar pattern as hardhat-slang-solx by marianfe · Pull Request #8658 · NomicFoundation/hardhat

marianfe · 2026-10-01T15:52:15Z

This PR adds initial support for the new slang compiler by following the previous hardhat-slang-solx plugin added in #8034.
The PR reuses the core hardhat swappable compiler type support added in #8008 and #8009.

hardhat-slang adds slang as a compiler type, and follows the same pattern of requiring adding a slang build profile to hardhat.config.ts.
Note that the compiler version is now decoupled from the Solidity language version, so the plugin configuration pins the slang version to download in slang.version , whereas the build profile specifies which solidity versions to be compiled with slang (currently, we aren't passing the Solidity version to slang, and compiler 0.8.x version support is not ready, see limitations). Same EVM versions supported as the previous hardhat-slang-solx.

Current limitations (will be addressed in follow-up PRs):

tested by successfully building real repositories (such as OpenZeppelin) however, current pre-release slang version used here does not output ABI or DWARF, so the end-to-end compiler tests in the EDR repo are not yet passing (support will be added in a next PR).
running hardhat test --build-profile slang will fail because EDR rejects build info without ABI.
Releases mirror is not yet set up, so the current setup uses the github releases page directly, will be updated in a future PR.
the compiler pre-release binary used in this PR currently builds everything as 0.8.37.
The solidity version will need to be passed to the slang binary when compiling (future PR).
EDR will require updates to support slang compiler type
EDR will need to parse DWARF traces / slang traces instead of solc AST to reconstruct stack traces etc.
compiler pre-release version used here also doesn't output metadata, which is also required by hardhat.
only verified on linux x64 for now, no MacOS, Arm, or Windows tests yet.

No changeset included as this plugin is not release-ready yet.

changeset-bot · 2026-10-01T15:52:24Z

⚠️ No Changeset found

Latest commit: af1b1fb

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github-actions · 2026-10-01T15:54:19Z

hardhat

Total size of the bundle: 41M
Total number of dependencies (including transitive): 38

List of dependencies (sorted by size)

33M	total
7.3M	@sentry/core
5.2M	zod
3.8M	micro-eth-signer
2.2M	undici
2.2M	@noble/curves
1.8M	@noble/hashes
1.4M	@nomicfoundation/hardhat-utils
1.1M	@noble/ciphers
884K	@nomicfoundation/hardhat-vendored
792K	@streamparser/json
692K	@nomicfoundation/hardhat-errors
536K	@scure/bip39
508K	ethereum-cryptography
504K	tsx
468K	micro-packed
408K	json-stream-stringify
320K	enquirer
320K	@nomicfoundation/hardhat-zod-utils
292K	semver
216K	adm-zip
208K	@scure/base
204K	ws
188K	@streamparser/json-node
168K	esbuild
156K	@nomicfoundation/edr
152K	fast-equals
108K	@scure/bip32
100K	chokidar
72K	@nomicfoundation/solidity-analyzer
56K	rfdc
48K	ansi-colors
44K	resolve.exports
44K	readdirp
40K	p-map
24K	strip-ansi
24K	is-safe-filename
24K	env-paths
24K	ansi-regex

Copilot

Copilot review overview

🟡 Changes recommended

Custom binary build identity can cause stale cache hits, and the documented test command cannot work with the pinned prerelease.

Review effort: Balanced
Findings: 1 · 1

Open (2)

Preserve compiler build revision in longVersion to prevent stale artifacts · New
Remove failing hardhat test command from usage instructions · New

What changed in this PR

Adds the experimental @nomicfoundation/hardhat-slang plugin, modeled after hardhat-slang-solx, to integrate the new Slang compiler pipeline with Hardhat 3.

Changes:

Adds Slang configuration, compiler hooks, release validation, and output augmentation.
Implements verified compiler downloads and platform-specific asset selection.
Adds plugin documentation, errors, fixtures, and comprehensive tests.

File	Description
`pnpm-lock.yaml`	Registers the new workspace package.
`packages/hardhat-slang/tsconfig.json`	Configures TypeScript references.
`packages/hardhat-slang/test/slang-compiler.ts`	Tests compiler invocation and selectors.
`packages/hardhat-slang/test/platform.ts`	Tests platform asset naming.
`packages/hardhat-slang/test/output-augmentation.ts`	Tests DWARF output integration.
`packages/hardhat-slang/test/optimizer-mode.ts`	Tests optimizer defaults.
`packages/hardhat-slang/test/mirror-availability.ts`	Checks release assets and checksums.
`packages/hardhat-slang/test/integration.ts`	Tests plugin integration and coexistence.
`packages/hardhat-slang/test/hook-handlers/solidity.ts`	Tests compiler hooks and custom paths.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/package.json`	Defines debug-info fixture package.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/hardhat.config.ts`	Configures the debug-info fixture.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/contracts/InlineAsm.sol`	Adds inline-assembly coverage.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/contracts/Counter.sol`	Adds runtime-bytecode coverage.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/contracts/ConstructorRevert.sol`	Adds creation-bytecode coverage.
`packages/hardhat-slang/test/fixture-projects/with-debug-info/.gitignore`	Ignores fixture outputs.
`packages/hardhat-slang/test/fixture-projects/simple/package.json`	Defines the simple fixture package.
`packages/hardhat-slang/test/fixture-projects/simple/hardhat.config.ts`	Configures the simple fixture.
`packages/hardhat-slang/test/fixture-projects/simple/contracts/Greeter.sol`	Provides a basic fixture contract.
`packages/hardhat-slang/test/downloader.ts`	Tests downloading, retries, and verification.
`packages/hardhat-slang/test/config.ts`	Tests configuration resolution and validation.
`packages/hardhat-slang/src/type-extensions.ts`	Adds Slang configuration and output types.
`packages/hardhat-slang/src/internal/slang-compiler.ts`	Implements the compiler adapter.
`packages/hardhat-slang/src/internal/platform.ts`	Resolves platform asset names.
`packages/hardhat-slang/src/internal/hook-handlers/solidity.ts`	Implements compiler lifecycle hooks.
`packages/hardhat-slang/src/internal/hook-handlers/config.ts`	Implements plugin configuration hooks.
`packages/hardhat-slang/src/internal/downloader.ts`	Downloads and verifies compiler binaries.
`packages/hardhat-slang/src/internal/constants.ts`	Defines releases and supported settings.
`packages/hardhat-slang/src/index.ts`	Registers the plugin.
`packages/hardhat-slang/README.md`	Documents installation and usage.
`packages/hardhat-slang/package.json`	Defines package metadata and dependencies.
`packages/hardhat-slang/LICENSE`	Adds the package license.
`packages/hardhat-slang/eslint.config.js`	Configures linting.
`packages/hardhat-slang/.prettierignore`	Excludes generated files from formatting.
`packages/hardhat-slang/.gitignore`	Excludes generated package files.
`packages/hardhat-errors/src/descriptors.ts`	Adds Slang-specific errors.
`cspell.dictionary.txt`	Adds MLIR to the dictionary.

Files not reviewed (1)

pnpm-lock.yaml: Generated file

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+    `Could not parse slang version from --version output: ${versionOutput}`,
+  );
+
+  return match[1];


+Run tests or compile using the slang build profile:
+
+```bash
+hardhat test --build-profile slang
+hardhat build --build-profile slang


…ng config

…dity version

Copilot

Copilot review overview

🟡 Changes recommended

Compiler defaults, custom-binary identity, release automation, and CI coverage contain unresolved correctness issues.

Review effort: Balanced
Findings: 2 · 3 · 2

Open (7)

Add missing CHANGELOG.md before package release · New
Preserve compiler build revision in longVersion to prevent stale artifacts
Unset evmVersion selects unsupported Solc target · New
Align empty compiler path handling across hooks · New
Add CI coverage for pinned release assets and checksums · New
Use origin-neutral wording for status failures · New
Remove failing hardhat test command from usage instructions

Files not reviewed (1)

pnpm-lock.yaml: Generated file

+  "files": [
+    "dist/src/",
+    "src/",
+    "CHANGELOG.md",


+    settings: {
+      ...settings,
+      // Defaults added here instead of in SlangCompiler.compile so this reaches
+      // the solcInput and hence the build-id hash.
+      optimizer: {
+        ...optimizer,
+        mode: optimizer.mode ?? DEFAULT_SLANG_OPTIMIZER_MODE,
+      },


+    const needsDownload = compilerConfigs.some((c) => {
+      if (c.type !== SLANG_COMPILER_TYPE) {
+        return false;
+      }
+      if (c.path !== undefined) {
+        log(
+          `Skipping download for Solidity ${c.version}: custom path provided`,
+        );
+        return false;


+  // Opt-in: run by the path-filtered mirror-availability job in ci.yml,
+  // not on every PR that rebuilds this package.
+  { skip: process.env.HARDHAT_RUN_MIRROR_TESTS !== "true" },


+function describeChecksumRequestFailure(error: Error): string {
+  if (error instanceof ResponseStatusCodeError) {
+    return `the mirror responded with status ${error.statusCode}`;
+  }


nebasuke · 2026-10-04T12:34:06Z

As a heads up I'm adding --solidity-version <version> and settings.solidityVersion in NomicFoundation/solx#787.

Claude comment

NomicFoundation/solx#787 takes the Solidity version from settings.solidityVersion in standard JSON mode and rejects --solidity-version next to --standard-json, the same way it handles --evm-version. Could augmentIfSlang set solidityVersion: entry.version alongside the optimizer and debug-info defaults instead? Then it's in the solcInput, so the build info reproduces the compile on its own, and targetVersionFlag/targetSolidityVersion can go.

Claude example:

  return {
    ...entry,
    settings: {
      ...settings,
      solidityVersion: entry.version,
      optimizer: {

A solx without #787 ignores the unknown key and compiles at its latest version, as it does today.

We don't mark the package as private (this is to allow local testing via verdaccio). However, we do exclude it from release in the publish scripts. The release builds its publish list from a pnpm publish dry run, so excluding the package there keeps it out of every later step. The local command for regenerating that list gets the same exclusion. This crude filter will be reverted, likely when we merge `hardhat-slang` into core as a built-in plugin.

Copilot

Copilot review overview

🔵 Needs a closer look

Custom binaries can receive incompatible arguments, config hooks load compiler internals eagerly, and the mirror test is not enabled in CI.

Review effort: Balanced
Findings: 2 · 3 · 2

Open (7)

Add missing CHANGELOG.md before package release
Preserve compiler build revision in longVersion to prevent stale artifacts
Add CI coverage for pinned release assets and checksums
Align empty compiler path handling across hooks
Unset evmVersion selects unsupported Solc target
Use origin-neutral wording for status failures
Remove failing hardhat test command from usage instructions

Files not reviewed (1)

pnpm-lock.yaml: Generated file

Previously missed (2)

In code that hasn't changed since last review

Avoid importing compiler dependencies in config hooks

packages/hardhat-slang/src/internal/hook-handlers/config.ts:36

This config hook statically imports slang-compiler.ts, which in turn imports hardhat/internal/solidity and its compiler-execution dependencies. Config hook factories run on every Hardhat invocation, so commands that never compile still pay this startup cost. Move the output-selection constants/helper into a lightweight module that does not import the compiler runner, and import that module here.

Use custom compiler version for protocol metadata

packages/hardhat-slang/src/internal/hook-handlers/solidity.ts:151

A custom-path compiler is driven with metadata selected from the global pin rather than from the custom binary whose version was just parsed. Once releases have different CLI protocols (for example, a newer release with targetVersionFlag), pinning an older downloadable release while using a newer custom binary sends the older release's arguments and can compile the wrong Solidity target or be rejected. Select protocol metadata using customSlangVersion when known, and define an explicit fallback for unknown/nightly versions instead of letting slang.version control the custom binary.

…file main moved prettier to 3.9.9, so merging it left the lockfile pointing hardhat-slang at a 3.9.8 entry that no longer exists. The lockfile is regenerated from main's, which also drops @typescript-eslint 8.70.0 entries nothing references.

Copilot

Copilot review overview

🟡 Changes recommended

Configuration defaults, empty custom paths, release validation, error wrapping, and mirror-test CI integration have unresolved issues.

Review effort: Balanced
Findings: 2 · 6 · 2

Open (10)

Add missing CHANGELOG.md before package release
Preserve compiler build revision in longVersion to prevent stale artifacts
Inherited keys bypass release validation · New
Empty path incorrectly treated as custom executable · New
Custom executable errors are not wrapped in HardhatError · New
Add CI coverage for pinned release assets and checksums
Align empty compiler path handling across hooks
Unset evmVersion selects unsupported Solc target
Use origin-neutral wording for status failures
Remove failing hardhat test command from usage instructions

Files not reviewed (1)

pnpm-lock.yaml: Generated file

+);
+
+const slangVersionType = z.string().superRefine((version, ctx) => {
+  if (!(version in SLANG_RELEASES)) {


+    }
+
+    // Honor custom path — skip version lookup and download
+    if (compilerConfig.path !== undefined) {


+      const customSlangVersion = await getSlangVersionFromBinary(
+        compilerConfig.path,
+      );


kanej

I have added an exclusion to our release scripts to avoid hardhat-slang, it has no npm package currently even if this exclusion was to fail.
I think we merge the plugin now, and continue with follow on PRs.

…ease check

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marianfe added no changeset needed This PR doesn't require a changeset no peer bump needed no docs needed This PR doesn't require links to documentation labels Oct 1, 2026

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marianfe added 5 commits October 1, 2026 18:06

Add hardhat-slang plugin scaffold copied from hardhat-slang-solx

80f6763

Add pinned slang release and Solidity range validation to hardhat-sla…

f5a237d

…ng config

Download the pinned slang release from its release-table row

64bce2c

Drive the slang binary with the release row's args and the job's Soli…

5a6baa3

…dity version

Document the hardhat-slang plugin and gate the debug-info test

4b63ff5

marianfe force-pushed the feat/hardhat-slang branch from 8a1901d to 4b63ff5 Compare October 1, 2026 16:08

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nebasuke mentioned this pull request Oct 4, 2026

feat(slang): add a Solidity version setting NomicFoundation/solx#787

Merged

kanej removed the status:triaging label Oct 5, 2026

Copilot AI balanced review requested due to automatic review settings October 6, 2026 14:39

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kanej added 2 commits October 6, 2026 14:47

Merge remote-tracking branch 'origin/main' into feat/hardhat-slang

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This was referenced Oct 7, 2026

Hardhat runs of the slang compiler have no Solidity stack traces NomicFoundation/solx#806

Open

feat(hardhat-slang): slang stack traces via debugSymbols, solidityVersion in settings #8691

Merged

marianfe changed the title ~~WIP: hardhat-slang: add support for the new slang compiler by following the hardhat-slang-solx template.~~ hardhat-slang: add initial support for the new slang compiler by following the hardhat-slang-solx as a template. Oct 14, 2026

marianfe changed the title ~~hardhat-slang: add initial support for the new slang compiler by following the hardhat-slang-solx as a template.~~ hardhat-slang: add initial support for the new slang compiler by following the hardhat-slang-solx as a template Oct 14, 2026

marianfe marked this pull request as ready for review October 14, 2026 18:31

marianfe changed the title ~~hardhat-slang: add initial support for the new slang compiler by following the hardhat-slang-solx as a template~~ hardhat-slang: add initial support for the new slang compiler on a similar pattern as hardhat-slang-solx Oct 14, 2026

marianfe added 2 commits October 14, 2026 20:45

Merge remote-tracking branch 'origin/main' into feat/hardhat-slang

1399b35

chore: regenerate the lockfile after merging main

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marianfe enabled auto-merge October 14, 2026 19:00

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marianfe added this pull request to the merge queue Oct 14, 2026

github-merge-queue Bot removed this pull request from the merge queue due to failed status checks Oct 14, 2026

marianfe added this pull request to the merge queue Oct 14, 2026

github-merge-queue Bot removed this pull request from the merge queue due to failed status checks Oct 14, 2026

chore: exclude the unpublished hardhat-slang from the merge-group rel…

af1b1fb

…ease check

marianfe added this pull request to the merge queue Oct 15, 2026

Merged via the queue into main with commit b059d56 Oct 15, 2026
243 checks passed

marianfe deleted the feat/hardhat-slang branch October 15, 2026 10:18

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hardhat-slang: add initial support for the new slang compiler on a similar pattern as hardhat-slang-solx - #8658

hardhat-slang: add initial support for the new slang compiler on a similar pattern as hardhat-slang-solx#8658
marianfe merged 11 commits into
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