accept JSON arrays for bake vars to preserve multiline values

Parse the vars input as a JSON array of strings, falling back to the
existing list parser when JSON parsing fails. Preserve multiline values,
whitespace, and literal quotes in each Buildx --var argument.

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

README.md

@@ -239,7 +239,7 @@ The following inputs can be used as `step.with` keys
 | `set`          | List        | List of [targets values to override](https://docs.docker.com/engine/reference/commandline/buildx_bake/#set) (e.g., `targetpattern.key=value`)                                                                                                                          |
 | `source`       | String      | Build source to use. Supports local path and [remote bake definition](https://docs.docker.com/build/bake/remote-definition/). With a local path, Bake runs from that directory, so all relative paths are resolved from it. See [Source semantics](#source-semantics). |
 | `targets`      | List/CSV    | List of bake targets (`default` target used if empty)                                                                                                                                                                                                                  |
-| `vars`         | List        | [Variables](https://docs.docker.com/build/bake/variables/) to set in the Bake definition as list of key-value pair                                                                                                                                                     |
+| `vars`         | List/JSON   | [Variables](https://docs.docker.com/build/bake/variables/) to set in the Bake definition as a list of key-value pairs or a JSON array of strings                                                                                                                       |
 | `github-token` | String      | API token used to authenticate to a Git repository for [remote definitions](https://docs.docker.com/build/bake/remote-definition/) (default `${{ github.token }}`)                                                                                                     |
 
 ### outputs

__tests__/context.test.ts

@@ -87,6 +87,50 @@ describe('getInputs', () => {
     expect(gitContextSpy).toHaveBeenCalledTimes(1);
     gitContextSpy.mockRestore();
   });
+
+  describe('vars', () => {
+    beforeEach(() => {
+      setRequiredBooleanInputs();
+      setInput('source', '.');
+    });
+
+    test('preserves line-based input parsing', async () => {
+      setInput('vars', 'TAGS=one,two\nJSON={"value":"a,b=c"}\nQUOTED="literal"\nEMPTY=');
+      expect((await context.getInputs()).vars).toEqual(['TAGS=one,two', 'JSON={"value":"a,b=c"}', 'QUOTED="literal"', 'EMPTY=']);
+    });
+
+    test('preserves JSON entries including multiline values and whitespace', async () => {
+      const vars = [
+        'DOCKER_METADATA_OUTPUT_TAGS=example/app:latest\nexample/app:main\n',
+        'DOCKER_METADATA_OUTPUT_LABELS=version=1.2.3\r\ntitle=example\r\n',
+        'DOCKER_METADATA_OUTPUT_JSON={"tags":["example/app:latest","example/app:main"]}',
+        'PADDED=  "one,two"=three  ',
+        'EMPTY='
+      ];
+      setInput('vars', `  \n${JSON.stringify(vars, null, 2)}\n  `);
+      expect((await context.getInputs()).vars).toEqual(vars);
+    });
+
+    test('preserves duplicate JSON variable entries in order', async () => {
+      setInput('vars', JSON.stringify(['VERSION=default', 'OTHER=value', 'VERSION=override', 'VERSION=final']));
+      expect((await context.getInputs()).vars).toEqual(['VERSION=default', 'OTHER=value', 'VERSION=override', 'VERSION=final']);
+    });
+
+    test('accepts an empty JSON array', async () => {
+      setInput('vars', '[]');
+      expect((await context.getInputs()).vars).toEqual([]);
+    });
+
+    test('falls back to list parsing when JSON parsing fails', async () => {
+      setInput('vars', '["KEY=value"');
+      expect((await context.getInputs()).vars).toEqual(['["KEY=value"']);
+    });
+
+    test.each(['null', 'true', '1', '"KEY=value"', '{"KEY":"value"}', '["KEY=value",1]', '[null]', '[["KEY=value"]]'])('rejects invalid JSON variable lists: %s', async value => {
+      setInput('vars', value);
+      await expect(context.getInputs()).rejects.toThrow('Invalid vars input: expected a JSON array of strings.');
+    });
+  });
 });
 
 describe('getArgs', () => {
@@ -103,6 +147,36 @@ describe('getArgs', () => {
     process.env = originalEnv;
   });
 
+  test('passes JSON variables as individual CLI arguments without changing their values', async () => {
+    const vars = ['DOCKER_METADATA_OUTPUT_TAGS=example/app:latest\nexample/app:main', 'PADDED=  "one,two"=three  ', 'EMPTY='];
+    setInput('source', '.');
+    setInput('no-cache', 'false');
+    setInput('pull', 'false');
+    setInput('load', 'false');
+    setInput('push', 'false');
+    setInput('provenance', 'false');
+    setInput('vars', JSON.stringify(vars));
+    vi.spyOn(Buildx.prototype, 'version').mockResolvedValue('0.31.0');
+    const toolkit = new Toolkit();
+    const inputs = await context.getInputs();
+    const definition = await toolkit.buildxBake.getDefinition({vars: inputs.vars});
+    expect(await context.getArgs(inputs, definition, toolkit)).toEqual(['bake', '--allow', 'fs=*', ...vars.flatMap(value => ['--var', value]), '--metadata-file', metadataJson, '--provenance', 'false']);
+  });
+
+  test('requires Buildx 0.31.0 for JSON variables', async () => {
+    setInput('source', '.');
+    setInput('no-cache', 'false');
+    setInput('pull', 'false');
+    setInput('load', 'false');
+    setInput('push', 'false');
+    setInput('vars', '["KEY=value"]');
+    vi.spyOn(Buildx.prototype, 'version').mockResolvedValue('0.30.0');
+    const toolkit = new Toolkit();
+    const inputs = await context.getInputs();
+    const definition = await toolkit.buildxBake.getDefinition({vars: inputs.vars});
+    await expect(context.getArgs(inputs, definition, toolkit)).rejects.toThrow('Buildx >= 0.31.0 is required to use the vars input.');
+  });
+
   // prettier-ignore
   test.each([
     [

action.yml

@@ -51,7 +51,7 @@ inputs:
     description: "List of bake targets"
     required: false
   vars:
-    description: "Variables to set in the Bake definition as list of key-value pair"
+    description: "Variables to set in the Bake definition as a list of key-value pairs or a JSON array of strings"
     required: false
   github-token:
     description: "API token used to authenticate to a Git repository for remote definitions"

src/context.ts

@@ -48,7 +48,7 @@ export async function getInputs(): Promise<Inputs> {
     set: Util.getInputList('set', {ignoreComma: true, quote: false}),
     source: await getBakeContext(core.getInput('source')),
     targets: Util.getInputList('targets'),
-    vars: Util.getInputList('vars', {ignoreComma: true, quote: false}),
+    vars: getBakeVars(core.getInput('vars')),
     'github-token': core.getInput('github-token')
   };
 }
@@ -171,6 +171,19 @@ async function getBakeContext(sourceInput: string): Promise<BakeContext> {
   };
 }
 
+function getBakeVars(varsInput: string): string[] {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(varsInput);
+  } catch {
+    return Util.getList(varsInput, {ignoreComma: true, quote: false});
+  }
+  if (!Array.isArray(parsed) || !parsed.every(value => typeof value === 'string')) {
+    throw new Error('Invalid vars input: expected a JSON array of strings.');
+  }
+  return parsed;
+}
+
 function noDefaultAttestations(): boolean {
   if (process.env.BUILDX_NO_DEFAULT_ATTESTATIONS) {
     return Util.parseBool(process.env.BUILDX_NO_DEFAULT_ATTESTATIONS);