detect duplicate id and section title by update-checks-doc script

scripts/update-checks-doc/main.go

@@ -90,7 +90,9 @@ func Update(in []byte) ([]byte, error) {
 	var inInput bool
 	var skipOutput bool
 	var count int
-	lnum := 0
+	var lnum int
+	anchors := map[string]int{}
+	sections := map[string]int{}
 	scan := bufio.NewScanner(bytes.NewReader(in))
 	for scan.Scan() {
 		lnum++
@@ -104,6 +106,10 @@ func Update(in []byte) ([]byte, error) {
 			}
 			section = l[3:]
 			log.Printf("Entering new section %q (%s) at line %d", section, anchor, lnum)
+			if n, ok := sections[section]; ok {
+				return nil, fmt.Errorf("section %q at line %d was already used at line %d", section, lnum, n)
+			}
+			sections[section] = lnum
 			anchor = ""
 			inputHeader = false
 			outputHeader = false
@@ -116,6 +122,10 @@ func Update(in []byte) ([]byte, error) {
 			if len(anchor) == 0 {
 				return nil, fmt.Errorf("id for <a> tag is empty at line %d", lnum)
 			}
+			if n, ok := anchors[anchor]; ok {
+				return nil, fmt.Errorf("id %q at line %d was already used at line %d", anchor, lnum, n)
+			}
+			anchors[anchor] = lnum
 		}
 		if l == "Example input:" {
 			log.Printf("Found example input header for %q at line %d", section, lnum)

scripts/update-checks-doc/testdata/err/duplicate_id.md

@@ -0,0 +1,37 @@
+<a id="hello"></a>
+## Hello
+
+Example input:
+
+```yaml
+on: push
+```
+
+Output:
+
+```
+This block will be auto-generated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
+
+This section causes no error.
+
+<a id="hello"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+```
+
+Output:
+
+```
+This block will be auto-generated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
+
+This section causes an error since same `id` is used.

scripts/update-checks-doc/testdata/err/duplicate_title.md

@@ -0,0 +1,37 @@
+<a id="hello"></a>
+## Hello
+
+Example input:
+
+```yaml
+on: push
+```
+
+Output:
+
+```
+This block will be auto-generated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
+
+This section causes no error.
+
+<a id="hello2"></a>
+## Hello
+
+Example input:
+
+```yaml
+on: push
+```
+
+Output:
+
+```
+This block will be auto-generated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
+
+This section causes an error since same section title is used.

scripts/update-checks-doc/testdata/ok/skip_output.in

@@ -22,3 +22,28 @@ This section will NOT be updated
 [Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
 
 Skip updating the output.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+<!-- Skip update output -->
+
+```
+This section will NOT be updated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#THIS_URL_WILL_BE_UPDATED)
+
+Skip updating the output.

scripts/update-checks-doc/testdata/ok/skip_output.out

@@ -22,3 +22,28 @@ This section will NOT be updated
 [Playground](https://rhysd.github.io/actionlint/#eNokyjEOhSAQRdGeVbzit2yA3XwMCVEzQ5x5sSDs3YxWtzhXpWDQetq1WkmAN/MocFEsh7NSnPn8h71k3oZ9F5DjLGhbV/zmBOUQvQVrPQEAAP//SLkdHQ==)
 
 Skip updating the output.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+<!-- Skip update output -->
+
+```
+This section will NOT be updated
+```
+
+[Playground](https://rhysd.github.io/actionlint/#eNokyjEOhSAQRdGeVbzit2yA3XwMCVEzQ5x5sSDs3YxWtzhXpWDQetq1WkmAN/MocFEsh7NSnPn8h71k3oZ9F5DjLGhbV/zmBOUQvQVrPQEAAP//SLkdHQ==)
+
+Skip updating the output.

scripts/update-checks-doc/testdata/ok/skip_output_and_playground.in

@@ -22,3 +22,28 @@ This section will NOT be updated
 <!-- Skip playground link -->
 
 Skip both the output and the playground link.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+<!-- Skip update output -->
+
+```
+This section will NOT be updated
+```
+
+<!-- Skip playground link -->
+
+Skip both the output and the playground link.

scripts/update-checks-doc/testdata/ok/skip_output_and_playground.out

@@ -22,3 +22,28 @@ This section will NOT be updated
 <!-- Skip playground link -->
 
 Skip both the output and the playground link.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+<!-- Skip update output -->
+
+```
+This section will NOT be updated
+```
+
+<!-- Skip playground link -->
+
+Skip both the output and the playground link.

scripts/update-checks-doc/testdata/ok/skip_playground.in

@@ -21,3 +21,27 @@ This section will be generated
 <!-- Skip playground link -->
 
 This skips playground link.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+
+```
+This section will be generated
+```
+
+<!-- Skip playground link -->
+
+This skips playground link.

scripts/update-checks-doc/testdata/ok/skip_playground.out

@@ -24,3 +24,30 @@ test.yaml:6:23: undefined variable "unknown". available variables are "env", "gi
 <!-- Skip playground link -->
 
 This skips playground link.
+
+<a id="hello2"></a>
+## Hello 2
+
+Example input:
+
+```yaml
+on: push
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo ${{ unknown }}
+```
+
+Output:
+
+```
+test.yaml:6:23: undefined variable "unknown". available variables are "env", "github", "inputs", "job", "matrix", "needs", "runner", "secrets", "steps", "strategy", "vars" [expression]
+  |
+6 |       - run: echo ${{ unknown }}
+  |                       ^~~~~~~
+```
+
+<!-- Skip playground link -->
+
+This skips playground link.