# Matrix Strategy: Support for Scalar Values and Template Expressions
## 🎯 Overview
This Pull Request implements support for **scalar values and template expressions** in matrix strategies. Previously, every matrix value had to be declared as a YAML array — a bare scalar like `os: ubuntu-latest` or `version: ${{ fromJSON(...) }}` caused silent failures. Now, scalars are automatically wrapped into single-element arrays, enabling the `${{ fromJSON(...) }}` pattern that is commonly used in GitHub Actions workflows for dynamic matrix generation.
## ⚠️ Semantic Changes
Two subtle behavior changes are introduced that are worth understanding:
### 1. Scalar matrix values now produce a 1-element matrix expansion
**Before this PR:** A scalar value like
```yaml
strategy:
matrix:
os: ubuntu-latest # no brackets
```
failed to decode as `map[string][]interface{}`, so `Matrix()` returned `nil`. The job ran **once, without any matrix context** (`matrix.os` was undefined).
**After this PR:** The same input is wrapped to `["ubuntu-latest"]`. The job runs **one matrix iteration** with `matrix.os = "ubuntu-latest"` set.
> **Impact on existing workflows:** Workflows that accidentally used bare scalars instead of arrays will now run with a matrix context where they previously did not. The functional result is usually the same, but `matrix.*` variables are now populated. This is considered an improvement, but is a semantic change.
---
### 2. Unevaluated template expressions fall back to a literal string value
The actual resolution of `${{ fromJSON(needs.job1.outputs.versions) }}` into an array happens **before** `Matrix()` is called — in `EvaluateYamlNode` inside `pkg/runner/runner.go`. This PR does not change that evaluation path.
If evaluation succeeds → the YAML node already contains a proper array → `Matrix()` decodes it normally.
If evaluation **fails or is skipped** (e.g., expression not yet resolved) → the scalar string is now wrapped as `["${{ fromJSON(...) }}"]` → the job runs **one iteration with the literal unexpanded string** as the matrix value.
> **Note:** The test `TestJobMatrix/matrix_with_template_expression` covers this fallback path, not the successful resolution path. The literal-wrap behavior is the fallback, not the primary mechanism for template expression support.
---
## 🔑 Key Changes
### 1. Flexible Matrix Decoding (`pkg/model/workflow.go`)
#### New Helper Function: `normalizeMatrixValue`
```go
func normalizeMatrixValue(key string, val interface{}) ([]interface{}, error)
```
- Converts a single matrix value to the expected array format
- Handles three cases:
1. **Arrays**: Pass through unchanged
2. **Scalars**: Wrap in single-element array (including template expressions)
3. **Invalid types** (maps, etc.): Return error to detect misconfigurations early
**Supported scalar types:**
- `string` — including unevaluated template expressions
- `int`, `float64` — numeric values
- `bool` — boolean values
- `nil` — null values
#### Enhanced `Matrix()` Method
**Before:**
```go
func (j *Job) Matrix() map[string][]interface{} {
if j.Strategy.RawMatrix.Kind == yaml.MappingNode {
var val map[string][]interface{}
if !decodeNode(j.Strategy.RawMatrix, &val) {
return nil
}
return val
}
return nil
}
```
**After:**
```go
func (j *Job) Matrix() map[string][]interface{} {
if j.Strategy == nil || j.Strategy.RawMatrix.Kind != yaml.MappingNode {
return nil
}
// First decode to flexible map[string]interface{} to handle scalars and arrays
var flexVal map[string]interface{}
err := j.Strategy.RawMatrix.Decode(&flexVal)
if err != nil {
// If that fails, try the strict array format
var val map[string][]interface{}
if !decodeNode(j.Strategy.RawMatrix, &val) {
return nil
}
return val
}
// Convert flexible format to expected format with validation
val := make(map[string][]interface{})
for k, v := range flexVal {
normalized, err := normalizeMatrixValue(k, v)
if err != nil {
log.Errorf("matrix validation error: %v", err)
return nil
}
val[k] = normalized
}
return val
}
```
**Key improvements:**
- Handles unevaluated template expressions as scalar strings
- Automatic conversion to array format for consistent processing
- Validation to catch nested maps and invalid configurations
- Fallback to strict array format decoding for backward compatibility
- Early nil check for strategy to prevent nil pointer panics
---
## 🎁 Use Cases
### Example 1: Template Expression in Matrix (primary motivation)
```yaml
jobs:
setup:
runs-on: ubuntu-latest
outputs:
versions: ${{ steps.version-map.outputs.versions }}
steps:
- id: version-map
run: echo "versions=[\"1.17\",\"1.18\",\"1.19\"]" >> $GITHUB_OUTPUT
test:
needs: setup
strategy:
matrix:
# EvaluateYamlNode resolves this to an array before Matrix() is called
version: ${{ fromJSON(needs.setup.outputs.versions) }}
runs-on: ubuntu-latest
steps:
- run: echo "Testing version ${{ matrix.version }}"
```
### Example 2: Mixed Scalar and Array Values
```yaml
jobs:
build:
strategy:
matrix:
os: [ubuntu-latest, windows-latest] # Array — unchanged
go-version: 1.19 # Scalar — wrapped to [1.19]
node: [14, 16, 18] # Array — unchanged
runs-on: ${{ matrix.os }}
```
### Example 3: Single Value Matrix
```yaml
jobs:
deploy:
strategy:
matrix:
environment: production # Scalar — wrapped to ["production"]
runs-on: ubuntu-latest
```
---
## ✅ Benefits
- ✨ **Feature Parity with GitHub Actions**: Supports template expressions in matrix strategies
- 🔒 **Robust Validation**: Detects misconfigured matrices (nested maps) early
- 🔄 **Backward Compatible**: Existing array-based workflows continue to work
- 📝 **Clear Error Messages**: Helpful validation messages for debugging
- 🛡️ **Type Safety**: Handles all YAML scalar types correctly
---
## 🚀 Breaking Changes
**Technically none in a strictly backward-incompatible sense**, but two semantic changes exist (see [⚠️ Semantic Changes](#️-semantic-changes-read-before-merging) above):
1. Scalar matrix values now iterate (previously they caused a `nil` matrix / no iteration)
2. Unevaluated template strings now produce a literal iteration instead of skipping
Both changes are improvements in practice, but downstream users should be aware.
---
## 📚 Related Work
- Related Gitea Server PR: [go-gitea/gitea#36564](https://github.com/go-gitea/gitea/pull/36564)
- Enables dynamic matrix generation from job outputs
- Supports advanced CI/CD patterns used in GitHub Actions
## 🔗 References
- [GitHub Actions: Matrix strategies](https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs)
- [GitHub Actions: Expression syntax](https://docs.github.com/en/actions/learn-github-actions/expressions)
- [GitHub Actions: `fromJSON` in matrix context](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix)
Reviewed-on: https://gitea.com/gitea/act/pulls/149
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>
Co-authored-by: Pascal Zimmermann <pascal.zimmermann@theiotstudio.com>
Co-committed-by: Pascal Zimmermann <pascal.zimmermann@theiotstudio.com>
Use `golangci-lint fmt` to format code, upgrading `.golangci.yml` to v2 and mirroring the linter configuration used by https://github.com/go-gitea/gitea. `gci` now handles import ordering into standard, project-local, blank, and default groups.
Mirrors https://github.com/go-gitea/gitea/pull/37194.
Changes:
- Upgrade `.golangci.yml` to v2 format with the same linter set as gitea (minus `prealloc`, `unparam`, `testifylint`, `nilnil` which produced too many pre-existing issues)
- Add path-based exclusions (`bodyclose`, `gosec` in tests; `gosec:G115`/`G117` globally)
- Run lint via `make lint-go` in CI instead of `golangci/golangci-lint-action`, matching the pattern used by other Gitea repos
- Apply safe auto-fixes (`modernize`, `perfsprint`, `usetesting`, etc.)
- Add explanations to existing `//nolint` directives
- Remove dead code (unused `newRemoteReusableWorkflow` and `networkName`), duplicate imports, and shadowed `max` builtins
- Replace deprecated `docker/distribution/reference` with `distribution/reference`
- Fix `Deprecated:` comment casing and simplify nil/len checks
---
This PR was written with the help of Claude Opus 4.7
Reviewed-on: https://gitea.com/gitea/act/pulls/163
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-committed-by: silverwind <me@silverwind.io>
* WorkflowDispatchConfig supports ScalarNode and SequenceNode yaml node kinds
* Avoid using log.Fatal
* package slices is not in golang 1.20
---------
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
* throw if `uses` is invalid
* update JobType to return error
* lint
* put //nolint:dupl on wrong test
* update error message to remove end punctuation
* lint
* update remote job type check
* move if statement
* rm nolint:dupl ... we'll see how that goes
---------
Co-authored-by: Casey Lee <cplee@nektos.com>
Change planner functions to return errors
This enables createStages to return `unable to build dependency graph`
Fix PlanEvent to properly report errors relating to events/workflows
This change does parse the different types of workflow jobs.
It is not much by itself but the start to implement reusable
workflows.
Relates to #826
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
* fix: rework `setupShellCommand`
* move all logic to separate function so we can test that later
* split `step.Shell` and `step.WorkingDirectory` setup into own funcs
* general cleanup of function
* use `ActPath` to not collide with checked out repository
* use `shellquote.Split()` instead of `strings.Fields()` for better command split
* replace single string concat with `fmt`
Signed-off-by: hackercat <me@hackerc.at>
* lint(editorconfig): ignore *_test.go due to mixed style
Signed-off-by: hackercat <me@hackerc.at>
* fix[workflow]: multiple fixes for workflow/matrix
fix[workflow]: default `max-parallel`
fix[workflow]: default `fail-fast`, it's `true`, not `false`
fix[workflow]: skipping over the job when `strategy:` is defined but `matrix:` isn't (fixes#625)
fix[workflow]: skip non-existing includes keys and hard fail on non-existing excludes keys
fix[workflow]: simplify Matrix decode (because I "think" I know how `yaml` works) (fixes#760)
fix[tests]: add test for planner and runner
* fix(workflow): use yaml node for env key
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
* Add outputs field to job model
* Add output interpolation for jobs
* Add otto config reference for interpolated job output values into 'needs' context
* Add output interpolation call after job has completed.
* gofmt
* Remove whitespace
* goimports
Co-authored-by: Casey Lee <cplee@nektos.com>
* Remove pwsh -login and add Pwsh test
* Add Shell Command Test for coverage
* 🧪 Move PWSH Platform definition to inline test, it can always be expanded out later
Reference: https://github.com/nektos/act/pull/660#discussion_r626171728
* Test MacOS Build for transient failure
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
