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Add support for the extends keyword #1306

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2585113
Add support for the extends keyword
SamuelFrost Sep 18, 2026
7c7d1ca
Add extendsMergeMode for combine vs override extends merging
SamuelFrost Sep 24, 2026
ff4be89
Add extends and extendsMergeMode integration tests
SamuelFrost Sep 24, 2026
c4e9697
Use spread semantics for extendsMergeMode override
SamuelFrost Sep 24, 2026
6302f11
Refine extends tests with fixtures and unit merge coverage.
SamuelFrost Sep 24, 2026
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Refine extends tests with fixtures and unit merge coverage. 
Remove extends up e2e tests and CI matrix entry; slim extends fixtures and colocate mergeDevContainerConfigs tests with imageMetadata.
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@SamuelFrost
SamuelFrost committed Sep 24, 2026
commit 6302f11bec4187cf04a84d7eb0f762e251d86ff7
3 changes: 1 addition & 2 deletions .github/workflows/dev-containers.yml
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Expand Up @@ -61,12 +61,11 @@ jobs:
"src/test/cli.podman.test.ts",
"src/test/cli.test.ts",
"src/test/cli.up.test.ts",
"src/test/cli.extends.up.test.ts",
"src/test/httpOCIRegistry.test.ts",
"src/test/imageMetadata.test.ts",
"src/test/container-features/containerFeaturesOCIPush.test.ts",
# Run all except the above:
"--exclude src/test/container-features/containerFeaturesOrder.test.ts --exclude src/test/container-features/registryCompatibilityOCI.test.ts --exclude src/test/container-features/containerFeaturesOCIPush.test.ts --exclude src/test/container-features/e2e.test.ts --exclude src/test/container-features/featuresCLICommands.test.ts --exclude src/test/cli.build.test.ts --exclude src/test/cli.exec.buildKit.1.test.ts --exclude src/test/cli.exec.buildKit.2.test.ts --exclude src/test/cli.exec.nonBuildKit.1.test.ts --exclude src/test/cli.exec.nonBuildKit.2.test.ts --exclude src/test/cli.extends.up.test.ts --exclude src/test/cli.podman.test.ts --exclude src/test/cli.test.ts --exclude src/test/cli.up.test.ts --exclude src/test/httpOCIRegistry.test.ts --exclude src/test/imageMetadata.test.ts 'src/test/**/*.test.ts'",
"--exclude src/test/container-features/containerFeaturesOrder.test.ts --exclude src/test/container-features/registryCompatibilityOCI.test.ts --exclude src/test/container-features/containerFeaturesOCIPush.test.ts --exclude src/test/container-features/e2e.test.ts --exclude src/test/container-features/featuresCLICommands.test.ts --exclude src/test/cli.build.test.ts --exclude src/test/cli.exec.buildKit.1.test.ts --exclude src/test/cli.exec.buildKit.2.test.ts --exclude src/test/cli.exec.nonBuildKit.1.test.ts --exclude src/test/cli.exec.nonBuildKit.2.test.ts --exclude src/test/cli.podman.test.ts --exclude src/test/cli.test.ts --exclude src/test/cli.up.test.ts --exclude src/test/httpOCIRegistry.test.ts --exclude src/test/imageMetadata.test.ts 'src/test/**/*.test.ts'",
]
steps:
- name: Checkout
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83 changes: 0 additions & 83 deletions src/test/cli.extends.up.test.ts
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151 changes: 27 additions & 124 deletions src/test/configContainer.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -7,9 +7,8 @@ import * as path from 'path';
import { assert } from 'chai';
import { URI } from 'vscode-uri';
import { getCLIHost, loadNativeModule } from '../spec-common/commonUtils';
import { DevContainerConfig, DevContainerFromImageConfig } from '../spec-configuration/configuration';
import { DevContainerFromImageConfig } from '../spec-configuration/configuration';
import { readDevContainerConfigFile } from '../spec-node/configContainer';
import { mergeDevContainerConfigs } from '../spec-node/imageMetadata';
import { Workspace } from '../spec-utils/workspaces';
import { nullLog } from '../spec-utils/log';

Expand All @@ -26,6 +25,15 @@ async function readConfig(relativePath: string) {
return readDevContainerConfigFile(cliHost, workspace, configFile, false, false, nullLog);
}

async function expectReadConfigError(relativePath: string, pattern: RegExp) {
try {
await readConfig(relativePath);
assert.fail('expected read to throw');
} catch (err: any) {
assert.match(String(err.description || err.message), pattern);
}
}

describe('readDevContainerConfigFile', function () {
it('can read a basic configuration file', async function () {
const configs = await readConfig('./src/test/configs/example/.devcontainer.json');
Expand All @@ -40,154 +48,49 @@ describe('readDevContainerConfigFile', function () {
it('can resolve an "extends" file reference', async function () {
const configs = await readConfig('./src/test/configs/extends/.devcontainer.json');
assert.isOk(configs);
const expectedConfig = {
name: 'Overrides',
image: 'mcr.microsoft.com/devcontainers/base:latest',
forwardPorts: [80, 443],
capAdd: ['SYS_PTRACE', 'NET_ADMIN'],
hostRequirements: {
cpus: 2,
memory: `${8 * 2 ** 30}`,
storage: undefined,
gpu: undefined,
},
remoteEnv: {
FROM_BASE: 'base',
OVERRIDE_ME: 'child',
},
features: {
'ghcr.io/devcontainers/features/docker-in-docker:1': {
version: 'latest',
moby: true,
},
'ghcr.io/devcontainers/features/go:1': {
version: 'latest',
},
},
};

assert.deepEqual(configs?.config.raw as any, expectedConfig);
assert.notProperty(configs?.config.raw as any, 'extends');
const raw = configs?.config.raw as DevContainerFromImageConfig;
assert.strictEqual(raw.name, 'Overrides');
assert.strictEqual(raw.image, 'ubuntu:latest');
assert.deepEqual(raw.forwardPorts, [80, 443]);
assert.deepEqual(raw.capAdd, ['SYS_PTRACE', 'NET_ADMIN']);
assert.strictEqual(raw.hostRequirements?.cpus, 2);
assert.strictEqual(raw.hostRequirements?.memory, `${8 * 2 ** 30}`);
assert.deepEqual(raw.remoteEnv, { FROM_BASE: 'base', OVERRIDE_ME: 'child' });
assert.notProperty(raw, 'extends');
assert.notProperty(raw, 'extendsMergeMode');
});

it('can resolve nested "extends" file references', async function () {
const configs = await readConfig('./src/test/configs/extends/.devcontainer.nested.json');
assert.isOk(configs);
assert.strictEqual(configs?.config.raw.name, 'Nested');
assert.deepEqual(configs?.config.raw.forwardPorts, [80, 443, 2222]);
assert.strictEqual((configs?.config.raw as DevContainerFromImageConfig).image, 'mcr.microsoft.com/devcontainers/base:latest');
assert.strictEqual((configs?.config.raw as DevContainerFromImageConfig).image, 'ubuntu:latest');
});

it('rejects a cyclic "extends" reference', async function () {
try {
await readConfig('./src/test/configs/extends/.devcontainer.cycle-a.json');
assert.fail('expected cyclic extends to throw');
} catch (err: any) {
assert.match(String(err.description || err.message), /cyclic "extends" reference/);
}
await expectReadConfigError('./src/test/configs/extends/.devcontainer.cycle-a.json', /cyclic "extends" reference/);
});

it('can resolve "extends" with extendsMergeMode override', async function () {
const configs = await readConfig('./src/test/configs/extends/.devcontainer.override.json');
assert.isOk(configs);
const raw = configs?.config.raw as DevContainerFromImageConfig;
assert.strictEqual(raw.name, 'Override merge');
assert.strictEqual(raw.image, 'ubuntu:latest');
assert.deepEqual(raw.forwardPorts, [443]);
assert.strictEqual(raw.init, false);
assert.deepEqual(raw.remoteEnv, { OVERRIDE_ME: 'child' });
assert.deepEqual(raw.features, {
'ghcr.io/devcontainers/features/docker-in-docker:1': {
version: 'latest',
moby: true,
},
});
assert.deepEqual(raw.hostRequirements, { memory: '4gb' });
assert.notProperty(raw as any, 'extends');
assert.notProperty(raw as any, 'extendsMergeMode');
assert.notProperty(raw, 'extends');
assert.notProperty(raw, 'extendsMergeMode');
});

it('rejects an invalid "extendsMergeMode" value', async function () {
const cliHost = await getCLIHost(process.cwd(), loadNativeModule, false);
const configFile = URI.file(path.resolve('./src/test/configs/extends/.devcontainer.invalid-merge.json'));
try {
await readDevContainerConfigFile(cliHost, workspace, configFile, false, false, nullLog);
assert.fail('expected invalid extendsMergeMode to throw');
} catch (err: any) {
assert.match(String(err.description || err.message), /extendsMergeMode.*combine.*override/);
}
await expectReadConfigError('./src/test/configs/extends/.devcontainer.invalid-merge.json', /extendsMergeMode.*combine.*override/);
});

it('rejects a missing "extends" file', async function () {
try {
await readConfig('./src/test/configs/extends/.devcontainer.missing.json');
assert.fail('expected missing extends to throw');
} catch (err: any) {
assert.match(String(err.description || err.message), /was not found/);
}
});
});

describe('mergeDevContainerConfigs', function () {
it('uses image metadata merge logic for overlapping properties', function () {
const base: DevContainerConfig = {
image: 'mcr.microsoft.com/devcontainers/base:latest',
init: false,
privileged: true,
forwardPorts: [80],
hostRequirements: {
cpus: 4,
memory: '4gb',
},
remoteUser: 'vscode',
onCreateCommand: 'echo base',
};
const overlay: DevContainerConfig = {
image: 'mcr.microsoft.com/devcontainers/javascript-node:latest',
init: true,
forwardPorts: [443],
hostRequirements: {
cpus: 2,
memory: '8gb',
},
onCreateCommand: 'echo overlay',
};

const merged = mergeDevContainerConfigs(base, overlay);
assert.strictEqual((merged as DevContainerFromImageConfig).image, 'mcr.microsoft.com/devcontainers/javascript-node:latest');
assert.strictEqual(merged.init, true);
assert.strictEqual(merged.privileged, true);
assert.deepEqual(merged.forwardPorts, [80, 443]);
assert.strictEqual(merged.hostRequirements?.cpus, 4);
assert.strictEqual(merged.hostRequirements?.memory, `${8 * 2 ** 30}`);
assert.strictEqual(merged.remoteUser, 'vscode');
assert.strictEqual(merged.onCreateCommand, 'echo overlay');
});

it('uses override merge when extendsMergeMode is override', function () {
const base: DevContainerConfig = {
image: 'mcr.microsoft.com/devcontainers/base:latest',
init: true,
privileged: true,
forwardPorts: [80],
hostRequirements: {
cpus: 4,
memory: '8gb',
storage: '32gb',
},
};
const overlay: DevContainerConfig = {
image: 'mcr.microsoft.com/devcontainers/javascript-node:latest',
init: false,
forwardPorts: [443],
hostRequirements: {
memory: '4gb',
},
};

const merged = mergeDevContainerConfigs(base, overlay, 'override');
assert.strictEqual(merged.init, false);
assert.strictEqual(merged.privileged, true);
assert.deepEqual(merged.forwardPorts, [443]);
assert.deepEqual(merged.hostRequirements, { memory: '4gb' });
await expectReadConfigError('./src/test/configs/extends/.devcontainer.missing.json', /was not found/);
});
});
11 changes: 0 additions & 11 deletions src/test/configs/extends-up-override/.devcontainer.json
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8 changes: 0 additions & 8 deletions src/test/configs/extends-up/.devcontainer.base.json
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8 changes: 0 additions & 8 deletions src/test/configs/extends-up/.devcontainer.json
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8 changes: 1 addition & 7 deletions src/test/configs/extends/.devcontainer.base.json
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
{
"name": "example configuration",
"image": "mcr.microsoft.com/devcontainers/base:latest",
"image": "ubuntu:latest",
"forwardPorts": [80],
"capAdd": ["SYS_PTRACE"],
"hostRequirements": {
Expand All @@ -10,10 +9,5 @@
"remoteEnv": {
"FROM_BASE": "base",
"OVERRIDE_ME": "base"
},
"features": {
"ghcr.io/devcontainers/features/go:1": {
"version": "latest"
}
}
}
6 changes: 0 additions & 6 deletions src/test/configs/extends/.devcontainer.json
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Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,5 @@
},
"remoteEnv": {
"OVERRIDE_ME": "child"
},
"features": {
"ghcr.io/devcontainers/features/docker-in-docker:1": {
"version": "latest",
"moby": true
}
}
}
8 changes: 1 addition & 7 deletions src/test/configs/extends/.devcontainer.override.json
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Original file line number Diff line number Diff line change
Expand Up @@ -9,11 +9,5 @@
"remoteEnv": {
"OVERRIDE_ME": "child"
},
"init": false,
"features": {
"ghcr.io/devcontainers/features/docker-in-docker:1": {
"version": "latest",
"moby": true
}
}
"init": false
}
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