58 lines
3.5 KiB
Markdown
58 lines
3.5 KiB
Markdown
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# V-5a — `Test-Json -SchemaFile` failure behaviour (local PowerShell)
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**Status**: CLOSED
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**Date**: 2026-08-20
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**Environment**: PowerShell 7.6.5, Windows 11, local workstation (Stage A1 — offline, no tenant)
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**Task**: T061
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**Pinned by**: [tests/Configuration/TestJsonBehaviour.Tests.ps1](../../../tests/Configuration/TestJsonBehaviour.Tests.ps1)
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## Question
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OTD-005 selected `Test-Json -SchemaFile` for layer 2 validation. The documented risk was that
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`Test-Json` reports schema failure inconsistently across PowerShell versions — returning `$false`,
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writing a non-terminating error, or throwing. Layer 2 cannot be written until the actual behaviour
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on the target build is observed rather than assumed.
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## Observed behaviour
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| Scenario | Return value | Error stream | Terminating? |
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| --- | --- | --- | --- |
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| Valid document | `$true` | empty | no |
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| Type mismatch (`"a": 123` against `"type": "string"`) | `$false` | 1 error: `The JSON is not valid with the schema: Value is "integer" but should be "string" at '/a'` | no |
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| Missing required property | `$false` | 1 error: `The JSON is not valid with the schema: Required properties ["a"] are not present at ''` | no |
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| **Schema file itself unparseable** | **`$true`** | 1 error: `Cannot parse the JSON schema.` | no |
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Exception type on the error record is `System.Exception` in every failing case — there is no
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distinct exception type to branch on, so the wrapper must branch on the message text or, better, on
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error presence alone.
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## Findings that shape the implementation
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1. **Non-terminating, not throwing.** With the default `$ErrorActionPreference = 'Continue'` the
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cmdlet writes to the error stream and execution continues, returning `$false`. It does not throw.
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`-ErrorAction SilentlyContinue -ErrorVariable` is therefore sufficient to capture failures, as
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the editor contract requires.
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2. **An unparseable schema returns `$true`.** This is the load-bearing observation. A wrapper that
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trusted the return value alone would report a configuration as schema-valid when the schema never
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ran. Layer 2 MUST treat "error variable is non-empty" as failure regardless of the return value,
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and MUST distinguish the `Cannot parse the JSON schema.` message so it can surface exit code 4
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(schema file not found or itself invalid) rather than exit code 1 (configuration invalid).
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3. **One error per violating location, but not exhaustive.** Two independent property violations
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yield two error records, each with its own JSON pointer. Deeper or nested subschema failures may
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still be reported as a single error at the outermost failing location. The wrapper therefore
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emits one finding per collected error rather than assuming a single one, and the author may still
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need more than one validation pass to see everything. That residual limitation is documented
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rather than worked around — full violation reporting would require replacing `Test-Json` with a
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third-party validator, which OTD-005 rejected.
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## Consequences recorded elsewhere
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- Layer 2 implementation: [src/Configuration/Test-PersonaConfiguration.ps1](../../../src/Configuration/Test-PersonaConfiguration.ps1)
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- Regression pin: `tests/Configuration/TestJsonBehaviour.Tests.ps1` fails if a future PowerShell
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build changes any row of the table above.
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- **V-5b remains open**: this observation is for PowerShell 7.6.5 only. The Azure Automation runtime
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version is unverified, and finding 2 in particular is version-sensitive. Re-run this probe there
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before Stage B (T116).
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