# 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>
* updates to support newer version of docker sdk
Bumps [github.com/docker/cli](https://github.com/docker/cli) from 24.0.2+incompatible to 24.0.4+incompatible.
- [Commits](https://github.com/docker/cli/compare/v24.0.2...v24.0.4)
---
updated-dependencies:
- dependency-name: github.com/docker/cli
dependency-type: direct:production
update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>
* feat: upgrade to go 1.20
* feat: upgrade to go 1.20
* chore: use go version from go.mod
---------
Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Use the -s (silent) flag so curl does not pass metainformation like
downloadspeed etc to bash.
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
* Prior to this change, the artifact server always binds to the detected
"outbound IP", breaks functionality when that IP is unroutable.
For example, Zscaler assigns the host a local CGNAT address,
100.64.0.1, which is unreachable from Docker Desktop.
* Add the `--artifact-server-addr` flag to allow override of the address
to which the artifact server binds, defaulting to the existing
behaviour.
Fixes: #1559
* added input flags
* added input as part of the action event and added test cases
* updated readme
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
* fix: support docker create arguments from container.options (#1022)
* fix processing of errors, add verbose logging, fix test
* disable linter for code copied from docker/cli
* fix all linter issues
* Add license info
* Add opts_test.go from docker/cli and required testdata
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
* fix: show workflow info even if on.push is not defined (#1329)
To fix listing of workflows in such cases list/graph filtering was split with planning.
Now act supports one of the following list (-l)/graph (-g) cases:
* show all jobs of loaded workflows: act -l
* show specific job JOBNAME: act -l -j JOBNAME
* show jobs of loaded workflows in which event EVENTNAME is set up: act -l EVENTNAME
* show jobs of loaded workflows in which first defined workflow event is set up: act -l --detect-event
For planning it supports:
* running specific job JOBNAME with triggered event determined from:
** CLI argument: act -j JOBNAME EVENTNAME
** first defined in loaded workflows event: act -j JOBNAME --detect-event
** only defined in loaded workflows event: act -j JOBNAME
** push event by default: act -j JOBNAME
* running jobs of loaded workflows in which event is set up, event is determined from:
** CLI argument: act EVENTNAME
** first defined in loaded workflows event: act --detect-event
** only defined in loaded workflows event: act
** push event by default: act
Except #1329 this PR fixes#1332, #1318
* Update docs/help
* Added documentation on how to pass inputs for workflows that require them
* Added the correct command to trigger the workflow
Co-authored-by: Casey Lee <caseypl@amazon.com>
* feat(#1161): add --through-action to assigned actions from GitHub
* docs(flags): add --through-action and --through-action-token flags description
* test(action, remote): add test case for ThroughAction
* refactor(command): rename command from --through-action to --actions-from-github
* refactor(command): rename command from --actions-from-github to --replace-ghe-action-with-github-com
* deps: bump go.mod to go1.18
* deps: go mod tidy
* docs: update Go version requirement
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
* docs: Expand the GITHUB_TOKEN section
* docs: Add a note on leaking GITHUB_TOKEN through shell history
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
